Update
I finally had some time, and cooler weather, where I could test fit some different line options on my 80. Here are the problems we face:
-finding the fittings to be able to build the lines from scratch is cost prohibitive.
-getting the R12 lines new from Toyota is no longer possible.
So here are the two options I can offer:
1) Send me the lines for
both an R12 and R134 system and I'll splice (braze) the R134 ends on the R12 lines, add a new Denso drier, o-rings and a new trinary switch to replace the R12 one with specs for R134. Cost for this option is $120. plus freight. You will either need to get a factory bracket or fabricate one to support the drier. This setup is what Kbahus and CycloSteve have for their rigs.
2) Send me your R134 lines, and I use those ends to build a new line from the drier to the condenser. This line is a 1-piece line, rather than a 2-piece like the factory R12 line is. I also build a new section from the switch port to the drier, again using the original R134 fittings. See pictures below and bear in mind I wasn't concerned about making the trial set of lines real pretty. With this setup, you can use the original trinary switch and a 1" shorter drier. You'll need a simple "L" bracket and hose clamp to support the drier. Cost for this option is $189 plus freight and includes the line fabrication, drier and o-rings. A larger than stock battery may not allow enough space for this set-up to fit.
I'm working on a set of instructions, although this is really a

+1/2 job. Make sure that the A/C system is empty. Cap off any open ends that you're not working on. You will need to remove the battery, battery box and grille to be able to maneuver the lines into position. Start with the line from condenser to drier. Gently work it from the top, through the oval shaped hole in the core support. Once it's in position, re-install the bolt on the condenser fitting. Now the battery box can go back into position but don't bolt it down yet. Then install the line from drier to fender connection. leave the fender connection loose, so the line can be positioned correctly. Remember that these are small diameter aluminum lines, they bend easily, so take your time. With both lines in place you can install the drier. Now you can tighten the fittings, again, these are aluminum, so don't overtighten. I installed the switch prior to installing the lines, be sure to snap the wire harness back onto it. With everything in place, snap the fender line back into the brackets (these are plastic and easy to break). Bolt down the battery box, re-install the battery and grille, then it's vacuum the system and re-charge.
There are bound to be questions, so you can either PM,
email or call me (Rex) @ 1-888-438-9534