273 LA bored .040 change in performance?

With no other changes;
Switching from a solid lifter FT cam, to a FTH hydro with same after-lash .050 numbers, the hydro will loose some bottom end torque, about 1.2 to 1.5 psi per degree later advertised, Ica.
If at the same time you go one size bigger on the intake duration of the FTH cam, you could easily lose enough pressure to make the bottom end noticeably soft. The only cures are more compression ratio or a tighter LSA. The band-aids are a higher stall TC and more TM (Torque Multiplication).