Magnum Intake on LA engine?

I think you can probably bolt in a Lean Burn distributor in to a Magnum block (or your 273) and that would supply the "normal" signal that MS could work with. I'm running one of those on my 340 and it's keeping the GM EFI controller happy (90-92 Z-28, batch-fire MPI).

If I was in your shoes and was interested in keeping the 273, I'd look close at what the Maggie heads really were going to do to the CR. I suspect that it's not that big of a hit to the CR if any, and the ports are SOOOOOO much better you'd more than make up for any HP lost due to the lower CR. Maggie heads are on my list of things to do to my 340 - if I don't ditch it all together for a 4.7L HO or a 3G Hemi. Neither of those will be any time soon, I need to get the 340 tuned first.

Clair