It is very common on old use parts to have the intake manifold to not fit a different engine properly, I use a feeler gauge set to see how good or bad the intakes fit on most Mopar engine I build. Take the manifold and heads and make sure they are clean with no gasket material or silicone gasket maker on the gasket surfaces and set the intake on the heads, rock it back and forth and side to side and look down the manifold bolt holes to see if the intake bolt alignment to the heads is good or not and then use your feeler gauge to see how much gap you have at each corner at the top and bottom. I like to see no gap at the bottom on both sides and no more than .0030 (three thousands) gap at the top of the intake to the heads
Write the gaps down on each corner so you can take it to a good machine shop to have them machine and correct the face, if needed
My current 400 stroker bracket motor has right at .180 in gasket installed to seal the cut down intake to match those heads on that block
A lot of the tock OEM street hemi suck oil through the bottoms of the stock intake gaskets due to taper intake faces on the stock intake manifolds