Looking for some Differential advice

I’ve got 205-70-14’s on the front and 265-60-14’s on the rear. Not changing them. I have an offenheiser? Intake and a 2bbl Holley now. It’s a dog. It’ll do maybe 50 on the freeway going up hill. When I downshift it just bogs out. I have a 408 Stroker and a built 727 to run that rear end with. I just don’t want my car to sit for another year.
somethings off on your tune up!! wheres your initial and tottle timing at?? maybe carb needs tweeking to,..when last time valves been adjusted?