The stock bowl can be used even with a regulated return, and the Termy fits under the fuel bowl no sweat. The problem is that if you use the rest of the stock fuel lines, you may have clearance issues with the metal lines near the HPOP on the passenger's side engine valley. However, I believe a few people got it to work.
If you are upgrading the high pressure oil system, might as well do the regulated return too.
If you are upgrading the high pressure oil system, might as well do the regulated return too.