"drop in" small block

Its a 2bl with2bl pistons, LD4B, home spun port job on heads new comp cams kit 270s solid lifter (one notch above commando specs) double row timing chain and gears.
Im unsure of what stall the tc is. Stock 904 and 8 3/4.
If I was to drop in a 318 use the LD4B, I have a set of xheads with valves sitting on the shelf.
I then use the commando "cosmetics" from 273 to dress it up period correct.
The 273 runs good its just not got the commando pistons which seriously hurts it in my opinion?
Im open to ideas? Would like the swap done in a weekend and gain 50 HP
If your motor has the correct 10.5 piston in it just put a cam in it, If not then swap the motor. Just my 2 cents

Is the engine in the car, is it a commando engine or a 2 barrel engine?
67' Barracuda 273 (Camshaft Results at the Track)