I'm impressed by the amount of work you're doing making that ill-fitting kit into a nice model - my grandfather used to call that 'making chicken salad out of chicken....(well, you know).' I'd say remove the trim strips, as it's a hot rod anyway.
The pro street trend/movement was actually started to emulate the pro/stock drag cars, and those huge rear tires need to be within the stock body width; a narrowed rear end is a must. Roll bars and engine size on a street car, unlike the drag cars, are entirely up to the builder. A few builders even did up FWD cars as pro streeters, while maintaining the original FWD drivetrain.