Glenn,
I agree with your builder. The cam you have is mild for a 4" arm engine, but usable. In fact, you could upgrade to 1.6s and it would be perfect. In terms of heads, the LA RPMs would be ok and I don't think you'd be disappointed. Also, Indio Motoers is in CA and has a good head in the iron RHS MA-X or LA-X deals. Ready to bolt on for $1300 plus shipping and out of the box are around 240-250cfm. You wont get RPMs ready to install for that, nor any MP stuff.