The assembly is balanced to 28 oz's. So...I go with a 28oz flyhwheel from my 289, do I use a clutch/pressure plate assembly for a late model 5.0 or the original 289? Or simply is there no difference?
Clutch size has absolutely nothing to do with the year of the engine block. There are only three size clutch & pressure plates used on small block Fords-- 10, 10.5 and 11" I don't think the early long style pressure plates bolt up to a later diaphram style flywheel. Best to check that aspect. As for what size P/P you need, count the teeth on the flywheel, 157 tooth uses a 10 or 10.5 " clutch, 11" fits 164 tooth flywheels.
The flywheel is a 157 tooth 28oz balanced flywheel, the block is a 87 roller block. The old pressure plate was a diaphram style one. The 10.5 inch set-ups (pressure plate/clutch disk) I can find states that its for a 86-93 5.0 mustangs. The tranny is a 4 spd toploader