will new clutch fit bellhousing?

'68 383 barracuda with '71 A833 - took out old clutch (BB type) that had a 10.5" clutch disk - the old PP appears to measure 10" across the turned surface. Somewhat of a mismatch with disc edges extending a bit beyond the PP turned surface. Bell is 2892513. Want to replace with a RAM 10.9 clutch that comes with a 10.5 disc. The bolt pattern measurements are the same (11 5/8"). Wondering if bellhousing will still fit. Another question is how pressure plate sizes measured - across the turned contact surface or some other diagonal? Any comments much appreciated. am I overthinking this as ususal ?