On boats, the B20 lasted until the early 80s as the
AQ130 (the B18 seems to be an AQ115 and the B30 was
AQ170). Boat places are still a good place to find
some of the weirder things that one may want, such as
the thick head gaskets for reducing the compression
ratios. For example,

http://216.37.204.206/Actionsports/Volvo_oem/Volvo.asp?Type=13&A=5&B=18


the head gasket kit part number 876783-2 will reduce
the B20's compression ratio to 8.4, so this thing looks
like it is the same as the IPD "lower compression ratio"
head gasket, but you get a whole kit from this place
and it is cheaper than the gasket by itself from IPD.
Their B30 gasket kits look to be cheaper than from other
places as well.

Boat part resellers often have better exploded diagrams
than car places. There is even a picture (line drawing) of
the triple SU intake manifold for a B30 at
https://www.onlinemicrofiche.com/OEM_Images/Volvo_images/3685_1H19.gif


fun stuff,
chris