I usually think the owner should get to make these decisions, but since you asked and its your truck I say keep the six. If it were my truck I'd probably be thinking V-8.

I'm putting a 500 Cadillac in mine.

1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble...