84 Pick-up: With a 4 inch suspension lift, can I fit 35's, or will I need a BL also?

 

That depends. Does your suspension lift actually add suspension travel or does it just lower the suspension away from the frame? If you are not adding much or any travel than you can probably squeeze 35's in there with the possibility of minor fender trimming. If you have a Marlin or similar kit that adds flex you will need to clearance the fire wall or move the axle forward and maybe modify the fenders and bedsides. If you plan to stuff 35's at full compression you will need to do as much cutting as you'd have to to fit 35's with no lift at all.