"drop in" small block

You are correct in thinking the 2bbl pistons combined with that 270s & 3.23's are really hurting the low end/throttle response! I bet it starts to move around 3000-3200rpm but soft below that? The (lack of )higher compression is most definitely whats hurting you, combined with stock 1800-2000 tops stall ttorque converter & 3.23's. Those domed slugs make a BIG diffrence my friend!