Yes capacity makes more torque, but heavier parts use it up again. The guy is asking about stock engines using a C cam. In both cases the limiting factor is firstly the cam & secondly the cylinder head. The bored out/high performance R-sport engines you speak of use a drastically modified cylinder head.

My engine building experience is not limited to Volvo engines.

Mine neither. I've rebuilt GM's as large as 645 cubic inch/cylinder & GE's that run all day at 28psi of boost.... big deal

I built a 427 Ford Cobra replica a few years back. I thought the 427 was a bit small, and very expensive. I built a 460 cubic inch engine

I have a customer who has a Marcos powered by a B18 with one of my camshafts that regularly beats genuine 427 Cobras at events. I'll bet it would beat your 460 Cobra too because anything with that much iron of the front axle is only good in a straight line.

I'd still go with the B20, which until 1974 had essentially the same rods as the B18.

You obviously haven't done much with B18's because they have lighter rods than the early B20's even though they use the same bearing.