383 power upgrade help

273 said
Trick flow states this for the 240 on their website. "Longer than stock pushrods may be required. Minimum bore size is 4.320 in."

Humm, that’s weird because 2.19 + 1.76 = 3.95.

4.320 - 3.950 = .370
4.250 - 3.950 = .300

Not enough room for a 383 bore? Makes me wonder where the valve are sitting.