The Transgo kit is the only one I'm aware of as well... I use it in my Riviera for drag race purposes. It does a nice job. I have over 500 1/4 mile passes on my 325 4L and it's just now starting to give up. I'd say all in all, that's a success. I used Raybestos Blue plate race clutches, the transgo kit and the normal soft parts & steel kit. That's it.
I've run the non-lockup 9" art carr, a 10.5" TCI and so far, I think the 9" was my favorite.
Looks like we only have one choice then, too bad some of the 325-4l internals aren't the same as the 2004r (excluding the chain and trans case), something must be different with the valve body assemblies as well? To turn a 325-4l to a manual valve body is probably not possible because of the design difference, a manual shift 325-4l auto would be the set up for my long term project (not a Riv).
I was never able to find the Hemmings issue that had (is it Bruce Wellings?) Riviera article, would like to see what mods he made. I am doing some myself to my 85 T Type Riv and hope to share the outcome here soon, with pics. For now the upgrade is to 86-7 GN spec, though with a twist to "fit" the Riv.
Just bolting 86-7 parts up doesn't just work, passenger header won't clear frame, and there is no room to run the downpipe (with the AC box), by mounting an 86-7 passenger header on the Riv driver side of motor, the 86-7 turbo and heat shield fits with clearance and looks factory installed between engine and firewall) compressor housing is rotated 180 to point towards front of car. That's easy, further, the 86-7 intake bolt on is also easy, one simple mod to the Riv alternator bracket allows the use of the Riv original accessories including PS pump for Hydroboost. Riv engine wire harness is still used with a few mods, Casper ignition coil converter, boost solenoid, TPS, IAC wire re-routing, etc.
Working 86-7 factory intercooler issues, will not just bolt up, inlet IC inlet is on wrong side for turbo as mounted above, so cut off inlet pipe much lower than for a Duttwieller install to change, however may make it front mount as 86-7 IC fan will not clear Riv motor mount, and using IC scoop doesn't quit look like it belongs on the Riv, plus poor airflow etc. etc. in engine compartment.
The hard part of all the above is really just the plumbing as nothing is available for this, it is sure good to be able to fabricate and weld here! I am using the factory Riv passenger header as is, no mods to it. The factory 86-7 GN passenger header required mods, using two 2" ss weld els, a new crossover tie in was made at the turbo flange, the original crossover tie in flange of the 86-7 pass header was cut off and hole capped, then the flange was welded to the ss weld el (pics here in the future). Crossover pipe was made from 86-7 crossover, with a few cuts and reweld to run over the top of trans as the factory Riv set up only bigger diameter.
Downpipe was made like crossover, a few cuts and welds to 86-7 downpipe and it snakes down towards driver side firewall and down through just enough room with clearance ( allowing for heat ) to the cat.
Anyway that is a summary of my mods, pictures will work much better here as soon as I can. It really is going well, I did paint the frame and suspension, painted motor gray, details will be aluminum and black, and overall it has A nice clean factory look to it, now if I could just get moving a little faster on it, I am not too fast on my hobby stuff.