The best thing to do is talk to the builder that ported the cylinders if you can. My old 350 had some extensive porting and we dropped a +4 in it with mo problems. But you should find out for sure before doing so. Your best bet for the head is to run a cool head with domes set up for your application. Stroker, compression, etc. With that you won't need a spacer plate. Good luck with the build!