I can answer some of these questions. Yes, some red blocks had carbs - maybe only Canada and Europe. I have read general articles of red block making 400 HP with Turbo and excessive fuel to prevent detonation. Not fuel miser, but lots of HP. A 6 speed Tremec trans could probably be installed with ma...
FULLY charge the battery and then try again. Modern Volvos and others will not start unless voltage is good. Cranking speed is now a poor indicator of battery condition for starting.
2001 P2 (and maybe a couple later years) had transmission software to shift to neutral whenever you stopped in drive. It was like a early version of automatic engine shut off while waiting at a stop light. To get rid of it, you needed a dealer reprogram. My 2001 V70 still has this original software....