87GT+70mach1

I own a 87 GT and it is stock except flowmaster. I will bump the timing, remove the air silencer, probably get a short belt for the track.anyone know what l should run in the 1/4 with just these mods? anyway....I have chrome valve covers from my old 89and was going to put them on. since i am going to take the upper manifold off i will have to get a new gasket but if I got a upper to lower spacer would it help or hurt my performance(if so what size)- or can i not do it because of speed density?