Alright, after a lot of people talking and yapping about the whole 1SZ lifter being interchangable with the 4AGE shim-over-bucket design I finally got around to ordering 16 of the suckers to put in the race car. But first, a bit of a walkthrough about what you have to do in order to get to the point of being able to order them.
For the purposes of this guide i will refer to the standard shim-over-bucket design as either shims or buckets, while i will refer to the 1SZ solid bucket design as lifters.

1. Check Clearances
Ok just like you would be checking the clearances in order to install new shims when you install new cams, you will need to set shim clearances. Now there are two ways you can go about this.
Firstly, if you have lots of shims left over or hoarded from other things then you can shim up your engine in the normal way, and then use your micrometers to get the overall size of the shim/bucket setup. When you are measuring the thickness make sure you measure from the center of the shim/bucket assembly as there is a small nipple in the middle of the setup which sits on the valve, if you dont measure from the center you will get a wrong reading. This way is quite easy, but takes a fair while to do, and can cost more if you have to order in extra shims. Personally i went this route as i wanted to see the engine run before i ordered the lifters.
Secondly, if you dont want to go to the effort or expense of shimming up the engine completely and then pulling them all out again you can simply measure the thicknesses of the existing bucket/shim setup over each valve and then the clearance between bucket/shim and the cam. A simple bit of subtraction and addition will yield you with the correct thicknesses for the lifters.
A word of warning with this method, it is highly prone to error, and i suggest you do your maths two or three times, if not more. Personally i used this method for three of my shims/buckets which were out of spec when i orignally built the engine. Also this method can be infuriating if you have no clearance between a shim and the cam, and then have to start swapping out shims as per usual again. If you cant figure out the maths then i would suggest you never pick up micrometers again

2. Ordering the lifters
Ok, now that you have all your sizes nicely written down your next job is to wander off to Toyota and order all the lifters that you need (see end for part numbers). A word of warning though, they arnt cheap and rank in at about $18 a lifter at uber-special ex-employee trade price. All the part numbers should correspond nidely on the Toyota system now, and you should only have to wait about two or three weeks for them to come in (mine took about 7 weeks as they had to be added to the system).
Another word of warning regarding lifters in the larger sizes. The Toyota EPC will tell your friendly parts monkey behind the desk that there are compatible shims over the 5.68mm size. This is completely incorrect, i have two 5.74mm lifters which easily fit the entire 4AG bucket/shim assembly inside them (i will measure them up to see if they fit anything else). But you should be right so long as you havnt rebuilt your head too many times (like i have) and have short valves.

3. Installing the lifters
Ok, so its been the three or four weeks and now you have a package on your doorstep (oh how i love home delivery) with 16 (or more) lifters in it. Installing these is relatively simple, and if you managed to not misplace the sheet of thicknesses (i did) you can replace them off the sheet. If you did lose them you have to go back and measure them again to figure out what goes where.
Personally the entire exercise including measuring them again took me about an hour, and thats with a Coopers in my left hand, and yapping to people every 5min.
Note when installing new lifters you should use either a good engine oil, or moly grease and liberally coat the face of each lifter to ensure that they are lubricated on first start. Nothing worse than having a groove dug in one from a camshaft.

Ok, enough of the boring text, time for some pretty pictures. Firstly the lifters themselves:

And now some of them installed:


Now im sure you are questioning why in hell you would want to do this so here is a pros and cons list.
Pros:
  • Light (about 15g lighter)
  • No chance of flicking shims at high lift
  • Look pretty

Cons:
  • They cost a pretty penny


Thats pretty much it, simple isnt it...

Here is the lifter thicknesses and part numbers shamelessly stolen from Club4AG

13751-23030 　　　5.12
13751-23040　　　　5.14
13751-23050　　　　5.16
13751-23060　　　　5.18
13751-23070　　　　5.20
13751-23080　　　　5.22
13751-23090　　　　5.24
13751-23100　　　　5.26
13751-23110　　　　5.28
13751-23120　　　　5.30
13751-23130　　　　5.32
13751-23140　　　　5.34
13751-23150　　　　5.36
13751-23160　　　　5.38
13751-23170　　　　5.40
13751-23180　　　　5.42
13751-23190　　　　5.44
13751-23200　　　　5.46
13751-23210　　　　5.48
13751-23220　　　　5.50
13751-23230　　　　5.52
13751-23240　　　　5.54
13751-23250　　　　5.56
13751-23260　　　　5.58
13751-23270　　　　5.60
13751-23280　　　　5.62
13751-23290　　　　5.64
13751-23300　　　　5.66
13751-23310　　　　5.68

This guide brought to you by Garage Takai the home of semi-useless things which very few people have enough money to fund.
DISCLAIMER: Usual stuff, you break it, you bought it. Its not my fault if you cant wield a spanner or do simple ddition. Blah blah blah