I have an 87 quadzilla was wondering about some good mods. Already have cool head, pipe and 39mm carb.

 

What pipe do you have? Since you already have the basic mods, Id suggest porting, bore out your carb to 41mm. Thats about as far as you can go without getting funky, in which case id suggest a ton of porting, +6 swingarm, convert it to alky, and put it on about a 30lb diet.