Effect of Internal gearbox part damage

[east high]

What's a 40 piston head?

You'll get a bit more power if the new head has a higher compression ratio than your old head. You won't see any speed gains from the transmission that's for sure, just the ability to shift from first to second and second to first without double clutching.

[Les Parker]

Output ratios would be the same, so, if you take the lack of whine/noise from the errant gearbox into consideration, you may go faster due to the reduced (?) noise levels.

[antichrist]

Not only does the 6cyl take a shorter bell housing, the IIA and III have different clutches and clutch mechanisms so you'll have to deal with that as well.

[dabawei]

What's a 40 piston head?.

A little bigger piston head, new size will be 2.3 instead of 2.25 (WoW 0.05 extra, one more leg of horse )

[east high]

Oh.. okay. You're overboring the block. Got it.