440 tunnel ram

And here is where the trouble starts. If your race weight is 2200 pounds, you only need 450 hp to run 10s. Instead of buying aluminum heads and cam, you could rebuild the 440 with a reverse dome pistons set for 10:1 with .035 quench, mildly worked 452 heads with three angle valve job, a single four barrel, and a good hydraulic cam. If it were me, I would be looking at an aluminum head 340 or 360 build. Taking a 100 plus pounds off the front end would be a sizable performance improvement in itself. Want to be really different? Turbo slant six!
The problem with mopar is if you swap engine family you swap transmissions and start over completely. A rebuild with decent parts will blow past 450 hp and more torque than a small block and will be able to use transmission that is in place. I would imagine that parts arnt the easiest thing to come up with in the UK.