69 307 will also work. I run the 403 bell on my zz4 350 and mini starter. I replaced the oringinal w/ the GM mini/. I have the original starter and it is for a 153 tooth fly and 69 307 and will bolt up to the parallel bolt pattern on a zz4 350.
Does the Block have starter holes that line up parallel? If so, you should be able to find the correct starter.
69 X-44 base coupe, ZZ4, 16lb nodular flywheel, Center force DF clutch + PP, Holley 600DP, Hooker super comp 1 3/4 ceramics, 2.5" dual exhaust w/ X-pipe, flowmaster 40 series mufflers.