You need more cam with that converter and gears. I would look for a bigger cam, 230 duration @50, and around a .460 to .470 lift. One time I put a 280*(advertised)/.474 Mopar cam in a stock 318 and added a 4bbl. No issues with springs or too much lift. You loose lift with the stock rockers.
I would not run those gears, even if you up the cam some. I ran 4.30's behind a street 360, and then I changed out to 3.91's and the E.T. didnt' change at all. Nothing. I would go 3.23-3.55 gear.
I wouldn't run that converter with the engine you are doing. I would back down to even a stock 904 from a slant or 318. Just balance your flex plate.
You could sell the pieces you have and should have enough money to cover the cost of the changes.
