I'm swapping a carb converted L31 into my camaro and it doesn't look as though I can reuse the existing mechanical fuel pump. What should I use instead?

 

Find an EFI vehicle fuel tank and swap it in. Doesn't really matter what it came from. Put in a new electric fuel pump in the process, either a replacement TPI pump, or an aftermarket like Walbro 255 (very popular). You will need to use a return-type fuel pressure regulator up in the engine compartment, such as a Mallory 4309.

Or, you can put an in-line electric pump in. That would be best installed as close to the tank as you can get. Whether or not you need a regulator depends upon the pump you get. If it is a dead-head type regulator (which you should NOT use with an in-tank pump), you will need to make sure there is no clamped rubber line between the pump outlet and the regulator.

The factory 3/8" supply and 5/16" return lines are more than adequate for these tasks.

Some (not many) '86s had an in-tank electric pump installed. You might want to check to see if yours, by chance, does.

 

I ended up ordering an external electric designed to replace the mechanical on for carbs.

 

Mount it back by the tank, then.