I believe it is also possible to create an adapter plate similar to Pre '68 Dave's plate for the 41-55(ish) pumps to suit the earlier pumps (about 37 to 41) that have only one hole between the pump and block rather than two. I say that I believe it because I have built and installed a plate to do this but I have not run the engine using it to prove it truly works.
I wanted to use the older pump to make a closer match to the appearance of the 216 engines installed in Canadaian Military Pattern trucks. I also wanted to use the same bolt placements into the block as Dave's plate so that if my try turned out badly I could switch back to using his plate and the later pump but this made the clearance between body of the pump and the adapter quite tight in the area of the radiator hose connection to the pump where a bolt needs to go to secure the assembly to the block (just enough for the bolt head so that bolt has to be tightened slightly ahead of the others, clearance was helped by using a gasket between the pump and the plate and grinding an open end wrench to be thin enough to fit the gap). Another point to watch for on this is that one of the screws that threads into the lower part of the pump body needs to be a flathead like those at the top of the body to avoid interference between the bolt head and the block (unless you orient the bolt head so one flat sits against the edge of the water pump opening in the block, I chose to make all 4 screws theaded into the pump body flathead).
The pump is installed to the motor but I need to do some chassis work (brake lines and a new front crossmember to repair butchery by the PO) before putting the motor in the chassis to confirm that my water pump works as planned.
