~450hp from stock stroke 340?

Here go read this:

CamKing’s 355 boat motor cam

My 355" SBC boat engine
It's 10:1 with ported 492 heads, Performer RPM, and Holley 600.

RPM---TQ--BHP
3200--436--266
3400--443--287
3600--445--305
3800--444--321
4000--443--337
4200--440--352
4400--440--368
4600--441--386
4800--441--403
5000--432--411
5200--422--418
5400--412--423
5600--400--426

The cam is 216/220, on a 112 LSA, and 108 ICL

Its more than doable with that cam and carb in my opinion. Its only 1.32 HP per cube. Whether or not the OP has the ability to screw it together and make it work is another discussion all together.