I think I would go with the bolt in mount brackets and once you know everything is positioned where it needs to be (steering clearance , exhaust , distributor , etc.) you can weld 'em . I had clearance between the top of frame and bottom of manafolds when I first got my truck together and things eventually settled and the manafolds were hitting the frame. Very annoying ! Now I moved the engine forward (got the HEI off of the firewall) and up , also went with headers . Everything clears now !
