I swapped in a 460 in a 1975 Highboy and picked up some used Mad Dog fenderwell headers for it. I swapped a 460 in my 77 F-150 4x4 and used L&Ls. L&L said a body lift was required but I did not need one.
Mad Dog says I need a body lift for the Highboy and figured it was a similar situation. Well it looks like I need a body lift on this one. The steering u-joint is farther away from the firewall on the 250 vs the 150 which also makes the shaft lower and in the way. It looks like cutting the shaft up and moving the u-joint up against the firewall like the half ton would fix the problem. I'm thinking I might just sell the headers and go out the hood like I originally had planned. Anyone else find a solution for this?

 

Wish I had something for you. I have 460 L&L's in my 73 and Mad Dogs on my 390 in my 79...had no probs clearing either however I used a tilt in the 73 and the 73 column in the 79.

Post a pic so we can see your setup.

Wait...what engine perches are you using? My 73 had clearance issues with the front cab mounts coming off the frame. L&L engine perches lowered the engine and gave me the clearance I needed. Per L&L and worked like a charm.

 

I save pictures ,this here is co425 460 with the L&L headers ,stands ,and borgenson shaft ,,,,the borgenson shaft might be your solution.The lower pic is grinners with the borgenson shaft.

 

I don't have a pic on me but I'll work on that. See how far away the u-joint is away from the firewall. On my half ton with L&L's the u-joint is right up at the firewall which raises the shaft up in the rear.
I have the headers bolt up right now but I have the steering column loose, and pushed the steering wheel down and towards the center of the truck which moves the u-joint up and away from the engine. Its still hitting big time. There are no clearance issues with the cab mounts or any other part of the truck other than that steering shaft. This thing is going together on an extreme budget. Right now I'm leaning towards selling this exhaust set up and going through the hood. I also have basically brand new exhaust for these headers with Thrush welded mufflers (Flowmaster 40 knock off). That or cutting up my steering shaft and moving the u-joint up to the firewall is my other option so far.
I am running the trans dapt engine towers with stock 1979 2wd 460 mounts, sits in there perfectly. Hio hooked me up with them. I have some engine towers from a 1977 Highboy. Most of the bolt holes lined up with my frame but then I would need conversion mounts as well. I also have some towers from a 1979 F-250 4x4 and I think only 1 bolt hole on each side lined up.

 

That column in my pic would be from a 2WD before the tilt swap. If you want I could take some measurements and should have a spare 2WD column I could send your way. Like cheap!!! Like you pay the shipping cheap.