Input for 340 upgrades

Tti step headers, skip dougs.
Tune the distributor curve u less it's been done already. Seems like you'd have to pull the motor to really make striking differences
Head work would make more without changing mannerism.
If you get eddy heads, just change the cam, maybe to a roller, mild manners but accessing the flow of the heads .500-.550 would be a good 25hp perhaps more.
.480 and actual .460...you're not using the heads.

Cam , step headers and re tune.