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Eric

I just did that with an 1974 318. Couple of issues that I learned are.

Go with 360 vortec heads. These are the heart shaped champers. They give you a better fuel mix in the chamber.
To get compression up I shaved .40 off the heads and ported them to the intake. Otherwise you will lose power just bolting the 360 heads up to the 318 block.

If you use Magnum heads make sure they fit the intake that you got. Contrary to what you read they do not all just bolt up.
I have a older eldebrock performer intake maifold and I wanted to use newer magnum heads. But they would not bolt right up to old intake. The Bolt hole angles are different between the heads and the intake.

I added a hotter cam,oversized pistons 30 and MSD distributor, 600cfm carb with the older eldebrock performer intake.

Got 293 hp on the dyno.

Also noticed a 40hp drop using regular exhaust manifolds instead of performance headers.

I went with the 318 over the 360 one because I had it and knew it wasn't in too bad of shape, you do not have to change motor mounts and 318 is internally balanced vs the 360.

hope this helps and good luck

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Sounds like someone just came over from chevy land

Chrysler never made a vortec head. The magnum is kind of an equivelent in the mopar world but they have a way better chamber than a chevy vortec and flow even more. If the magnum heads are not what are being refered to as "vortecs" then who knows what is. The magnum is the only factory SB head with the heart shaped chambers.

You can use any old small block intake on a magnum head IF you redrill and tap the intake bolt holes in the head.

BTW No problem useing those two mismatched heads.