I'd like to swap my LO3 for an L98 sometime soon, and I'd like some pointers on how to do this RIGHT. I want to retain full stock functionality, cruise control, dual fans (with one computer controlled) etc. Any pointers?

 

Buy a complete engine and tpi wiring harness from 90-92, bolt it in, splice the vss wires so that they route appropriately, drive.

 

I've heard there were issues with the bulkhead connector in those swaps.

 

If your car listed in your info (91 RS TBI) is correct, and you get a 90-92 TPI with the correct 90-92 harness the only thing that is different in the bulkhead connector is that your vss wires currently go into the bulkhead connector and to a vss buffer box.

This will not be an issue as the TPI harness has the vss wires going to the ECU, the TPI harness simply has no connection at the pins in the bulkhead connector for the vss.

TBI cars have a buffer box, the vss wires go through the c100 bulkhead, across the dash to the buffer box, and then the buffer outputs the 4000 pulse signal to the gauge, 2000 to the cruise and ecu, the TPI cars have the vss signal going directly to the ECU, it then outputs the appropriate signals, the only changes you'll have to make are at the small C207 dash connector and vss buffer connector to get the signals for the speedometer where they need to be.

 

I did the swap and mine looks like a factory install. I put a 90 speed density TPI into a 92 TBI. Z28ricer is 100% correct. I know I had to wire in my reverse lights to the c100 since my car is manual and the harness was auto but I think that was the only reason I was in there. http://www.austinthirdgen.org/index.php?pid=19 These are diagrams that helped out a lot. Its pretty easy to sort out the speedo. Honestly its more work changing the fuel pump to the higher pressure one.

 

This was all really informative. Thanks guys

 

Do you have pics of your install?

 

These are 2 year old pictures and its looks a little cleaner and neater in there now but everything is there.