"And they're on all truck blocks whether 348 or 409's?."
All truck blocks, whether 348 or 409 have 2 notches. Both engines were rated at 7.75:1 CR.
"What's the whole story on the two notches in earlier blocks and one notch on the later blocks thing...two is worse?."
I don't believe that's accurate. Because of the 348's smaller bore, one notch was milled to provide exhaust valve clearance. With the standard piston (low perf), that produced 9.5:1 CR. For the hi-perf 348s with compression higher than 10:1 the piston dome was modified (raised) in the wedge area which made the combustion chamber smaller. Two notches are obviously worse, because you're starting with a base 7.75 CR. Even with hi-perf pistons, I doubt you could get to 9.0:1 CR.
"Do 409's always have the counterbalanced crank and the 348's the round one where the flywheel bolts on?."
As far as I know, all 348s have a round flywheel flange on the crank and all 409s have one that's asymmetrical.
"And are the distributors and waterpumps W-motor only or do SB or BB ones fit?."
Yep, they're W-motor only, along with the oil pump drive shaft due to the shorter distributor. The water pump bearing & shaft are the same as SB though, so there's no problem having them rebuilt.
Verne
