340 manifold vs TTI's which set-up?

No with those smaller step tti's they will work just fine. Go for it and sell the 340's... Someday you could always do a 1.88 by 1.60 valve job and maybe a little more cam to go with it. In either case I did hearers on mt Dad's 70 satalite years ago with a stock 318, only had a small 600 holley on a street dominator holley intake. The headers made it run much better. In fact I need to just do some minor carb jettng, so it did breather a bunch better than the stock iron ex. But the 340 ex are better than the 318 iron. I still would do the TTI's..