What issues to swap 350 to a 454

[cool breeze]

I have a 1979 K10 with a 350 and 700r4 transmission and wanting to put a 454 in it. Will the transmission bolt up without any issues? Will the flywheel and torque converter bolt up ok?
Also its a 1/2 ton frame and wanting to put headers on it, will they fit ok? What headers do yall recommend.

[JohnnyPopper]

350 and 454 have the same bell housing pattern, so that's an indicator that the spring plate/torque converter will conform.

Think about it like this: Car manufacturers engineered a continuity into their models that would allow a variety of different choices from consumers.

As far as headers, you will need to talk to the manufactures about mating their products with you specific model. Don't forget: a ball peen hammer may be your best friend...

[Swampyankee74]

If your small block is a 79 motor it will be a 2 piece rear main seal. Depending on the year of the big block it may be a one piece rear main seal. Which you would need a different flywheel or flex plate.

[Captkaos]

SBC are internally balanced (minus the 400) and BBC's are Externally balanced so the flexplate (for autos) and the flywheel (manuals) are not the same.
Dont expect the factory 700R4 to last very long behind the 454 unless it is fairly new or built to be installed behind it.  It will bolt up to it however.  BBC's were offered with TH400 auto.
The accessory mounts are completely different from SBC to BBC so you need the specific brackets for the BBC on what you plan to run.
If you are installing using the SBC engine mounts, your fan shroud probably won't work as it wont sit in the correct spot. 1.5" lower.
Keep in mind no 1/2T K-series truck ever came with a BBC from the factory.
I believe companies make BBC headers for K-series (its a popular swap) I would just verify fitment states 1/2T K-series.