Yes you can bore a 454. I think you can bore it out to a 468 or possibly more. But a 350 you can definitely build up to beat a slighty modified 454. Cam, bore, stiffer valve springs port and polish.. the whole nine yards. Car Craft did a thing on that like 2 years ago and the 350 cam out on top it was more efficient in $$$ and made just about the same power. also gearing matters in your rear. It can go on forever.
Justin
04 Trx 450r
85 Atc 350x
86 Trx 200sx
00 Xr 400R
85 Atc 70
98 Toyota Tacoma 4x4 xtra cab
99 400ex, 97 xr400, 85 Atc 110, 86 Atc 200x, 85 Atc 350X, 87 Trx 250X, 86 Atc 250R (mint), 78 Atc 90 all sold