My guess is that your 270 is later than '47, likely a replacement. There are 4 heads. #1 domed chamber with small ports. #2 H head domed chambers with large ports. #3 302 head D chamber for flat top pistons and has large ports . #4 Later ( around '55) 270 head different D chamber for flat top pistons and has small ports. #4 is probably what you need. Piston for the late 270s are hard to find but if yours are good find a head. These heads are the least desirable for performance but are fine for a street build.
Domed pistons are easier to find and you can use either domed head. Again for a street build the small ports work well. The large 1 3/4 ports can cause flow issues at low to mid throttle.
My 270 is a '57 and has the small port D chamber head. I built the engine in 1978 when pistons were easier to come by. It is in a 1/2 ton '53 Chevy pickup with a T-5 trans and a Dana 44 limited slip with 354 -1 gears. It will cruse at 70-80 all day.
