[leew67]

I have a 68 mustang convertible with a 390 and a c6 and am always looking for advice. Will my c6 bolt up to a 289 or 302 or would I have to also change the tranmission if I go with a small block.
Thanks In advance

[stlwagon]

We'll find you some answers in here.

[jim293]

Welcome go and check out the classics section. Have fun.

[RedGTvert]

Since no one else asked, why would you want to swap and FE for a small block?

[Cobrajet67]

I believe the c6 doesn't bolt up to the 90 degree small block(260, 289, 302/5.0, 351w). A c4 does though. Certain c6s bolt up to the 335 series small block(351c, 351m, 400c) but not your fe c6 I believe. I have to ask the same question as RedGTvert why would you ever want to downgrade to a small block if you have big block power already? The small block is great and all but you have a 390-that engine is a torque monster in a vintage mustang.

[Jay H 237]

I would go with a C4 if you get a small block. The C6 is 'overkill' if it did bolt up and not worth the parasitic loss.

The C4 losses 28 hp vs. 55-60 for the C6. The FMX is the least at 25 hp but the heaviest trans since it's in a cast iron case while the others are aluminum.