A coolant leak can be found with a pressure test of the coolant system. if it hold pressure...your OK one the coolant side.
Fuel issue should show up on both sides...if you have a typical intake manifold.
from the
oil side...could do a smoke test of the crankcase and see if any leakage into the intake/carb area.
what intake is on your car? is it a polished Aluminium Air Gap with no name cast on it? Next, is it a FMS 392 crate?...I think, back then, they came without intake and distributors...so, the assembler installed this stuff. I'm not a big fan of the Chinneezze knockoffs of the AirGap back then, some had some pretty bad QC if you know what I mean.
BTW...white smoke = coolant, blue smoke =
oil, black smoke = fuel