brian_wms said:
so let me get this right. All stock except intake, cam and headers, And I should be smokin right? bidding on a intake on ebay now.
All depends on your goals. That 307 HO cam isn't very good and was suggested to you only because your CR is very low ( though on a stock 403 I think you can still go a bit bigger ). If you want to go 'fast', all you need is a set of early 350 heads. These will bump up your CR ( more power ), allow you to run a better cam ( more power ) and flow better than the stock 403 heads ( again more power ).
An RPM intake is a good intake, but the standard Performer isn't going to do much of anything. Obviously true dual exhaust is a no brainer and yes headers will definitely help but you could always add headers ( and a better intake ) later on down the road since they are just simple bolt-ons.
So if I were on a strict budget, had a stock 403, and wanted some good get-up-and-go, I would get a set of decent older 350 heads ( with a good valve job if funds permit ), get a mild street friendly cam that matches well with my higher CR ( which I believe would be around 9 to 1ish ) and just run the stock intake and exhaust ( with true duals ) for now. I would then add an RPM intake and headers later on when I had more money saved. This all assumes I already have good gearing and a transmission that would last. If you don't have either of those things, you're looking at even more money. Going fast even on a budget isn't cheap!