First of 150k isn't that many miles especially if they are highway, i modded my 200k engine, yeah i chipped a piston but that was due to another reason. Personally i wouldn't worry about miles,again personal thought. These locks are great, all i would do is change any if not al gaskets that you see leaking, clean it, and get the work done right the first time. this is the hard part, you also have to decide how far into the BUILD you wan to get into, There are many things you can do to make it go faster, butt you have to decide what route, Rockers, Cam, I/C and such. as far as you're worry on engine miles brush it off, my worry would be the trans.
