I have a chance to obtain a '73 472 for a song and intend to swap it into my '79 deVille.

I have two questions to start out with.

I want to use a set of block hugger headers. What mods are needed to fit them in the '79 engine bay?

I still have the '69 modded intake - http://www.cadillacforums.com/forums/500-472-425-368/121589-intake-manifold-modification.html#post1295606

... as well as the AC compressor brackets to properly bolt up my '79 unit. Should I use it, or stick with the stock '73 intake?

Thanks guys. More to come (and pics) as this goes along.

Difficult to fit headers to this conversion. You have to physically check clearance because there is so little clearance between the exhaust ports and the upper control arms.

From what I am told , you should forget those headers... I believe MTS has some bolt in headers for your car... if not the best thing to do is get a set of BBC headers and weld on caddy flangers...as for the the early intake, it will work great... the rear compressor mount may be different.. if so, you will need one from the early intake.. If you got the motor out it is best to change the timing chain and gears... get rid of that plastic gear and put in a good roller chain set-up... no cheap ones, good ones are about $100

I tried the BB Chevy header route. Not worth the hassle in these cars! You really need to have custom headers made, since the BB Chevy have too many interferences with the '79s frame.
The block hugger headers I used only needed some slight mods to the drivers side to fit right.

Thanks for the help guys. Sounds like I'll just dispense with the headers.

Are there any compelling reasons to scrap the 425 exhaust manifolds for the 472 units? I know the earlier model is less restrictive, but is the gain worth the clearance issues/control arm mod?

It's real easy to just cut the excess bolt length off the passenger side A-arm, to allow the 472 manifolds to fit!