Quote Originally Posted by Quik View Post
to fit 8.1 youll need the front frame clip since the rails are shaped differently. wouldnt be a direct swap. best to start with a 3/4 ton 2wd truck

anything can work if bust out the torches and welders
I don't understand why would you need to do any frame work to fit an 8.1L in a GMT800 half-ton 2wd? The 8.1L has the same mounting as the old 7.4L, 5.7L and 4.3L V6. Being the 4.3L was an option in the GMT800, I don’t see why it wouldn’t bolt right in.

If you are thinking the A/C compressor would contact the frame, it just might. Just use GM medium duty truck, 2000-2002 3500HD or Workhorse Custom Chassis accessory brackets and move the A/C compressor to the driver’s side top of the engine and alternator to the passenger’s side similar to the L29 7.4L brackets. Same with exhaust manifolds. Any BBC exhaust manifold will fit the 8.1L. You would think one of them would fit the frame if the original 8.1L manifolds posed an issue in a halfton.

I dropped a 2002 8.1L into a 1978 K10 a while back and was surprised how easy it actually was. Used the same engine mounts, clutch and pressure plate from the 454HO that was removed as well as exhaust manifolds although I did use a specific 8.1L flywheel. The 8.1L is pretty much a direct bolt in. Mine is running on a Delphi MEFI-4 engine controller similar to the RamJet engines and marine engines. I may change it over to a MAF system sometime but so far I am happy with the speed density MEFI-4 system as it a much less intrusive wiring harness to deal with. This ’78 running a MEFI-4 controller on a custom calibration would run circles around the 454HO it replaced and definitley has a lot more nut than my stock 2001 Silverado 2500HD with an 8.1L.




A few YouTubes.
YouTube - Dirty Engine

YouTube - 8.1L mild launch

YouTube - Westcliff Stuck again

Install pictures is my sig.