[Jack21]

Changing the length of your driveshaft is not that big of a deal. Truck repair shops do this regularly, particularly in the snow belt for pickups used for snow removal.

If you're driving a West Coast with a 429 in it, one of the new Tremec T-600's may make for a far better trans than a T-5. (Not even sure you could find a 429 bellhousing for the T-5) The T-600 should fit your toploader bellhousing, and a replacement heavy duty driveshaft would be recommended.