Ok, I guess I am a dumbass when it comes to the search function, but I can't seem to find a definitive distance to locate SBC sidemounts into a deuce chassis. I have to get these things tacked in tomorrow morning and don't have access to a Chevy block to do a mockup until next weekend. From the front axle centerline, approximately how far back is it to the center mounting hole for a typical short water pump, HEI, SBC into a deuce? From there, how far back to the mount on a TH350? Stupid question, I know; this would all be done already if I had the engine and trans back from the machine shop on time ....
Get an engine with a distributor, water pump and fan, the transmission being used, and the firewall bolted in place, then locate it where everything clears.
Don't rush it or you'll be sorry you did. Nothing's worse that redoing it later. It always takes longer to do it twice. Way too many variables to just plug it in without having it all there to check all of the things listed below. Stock or .......... firewall? Type of radiator and core thickness? Mechanical or electric fan? An HEI is big, you might want to reconsider that too.
A Boner and Vintagehotrods gave the best advice. To do it right you need everything he described. Do it once and right. The FOGGER
Are there no scrap yards in your area? I could leave here at 8:30 in the morning and be back by 9:00 with a cracked block from a scrap yard. They usually have a pile of old transmission cases too. Getting there early in the a.m. is the key to getting them to sell you stuff, even if they are not supposed to.