Speed is $...
speed cost, how fast can you afford to go??? been said for years! you have spent some money but not really anything thats going to make more or better power than your 340 came new! after your headers what you got for exhaust?? cam converter and gears would be what id do, then if ya want more, intake and heads, maybe a stroker kit,..its a slippery slope,..the farther you slide the more it'll cost, but the faster it should go....cheapest way is to know where you want to end up, and do that,..buy once, cry once!!