You mean to the left of the distributor??
"A" is for 57-62 car 235 only. If the block does not have the 3 threaded studs cast in the sides of the block (like most V8's) then it is a '57 235 from a car. 58-62 blocks have provision for side motor mounts. Be aware, that 57 and earlier blocks that originally used solid lifters cannot use hydraulics because the lifter bores are not horizontally drilled for oiling. If it does have the drilling, then either cam can be used. Solids work better in these older engines anyway.
