318 Poly in an Early A Body?
You will have to modify the trans tunnel for a 727, not worth it in mho. You are on your own with headers, and a 4 barrel intake is rare and expensive. Then there is the small rear wheel wells. Any LA/ Magnum if done right will make an early Cuda Fly. Even with the stock 273 HP exhaust and manifolds. From 273 to 360. I've had one for 45 years.
Actually headers are now being produced, they are expensive, TTI, CCP and a couple others, but they’re about a 1000.
Factory 4 barrels can be had as low as 350 to as high as 750.
Dual quads and even six pack manifolds can be had for now much more.
Wieland, CCP and a few smaller outfits are selling brand new, aluminum 4 barrel intakes for about 600.
I'm wanting to say that the LA exhaust manifolds are not the same, so there's one more headache.
They are not. Port spacing is entirely different.
But the factory manifolds are rear dump and “should” clear
HOWEVER,
Factory Ford Mustang 5.0 GT Headers will fit with a minor modification to the bolt hole locations. However, they are unlikely to fit in an Early A body with out so tube modifications. But can be had for less than 50 bucks.
Also, if one really wanted, an LS7 intake has the exact same port locations and nearly the same shape and size as the poly. So with a simple spaced plate, one can put an LS7 intake on a poly.
It can be done cheap if one thinks outside the box
