GT40P heads on 289

I'm investigating the possibility of putting 5.0 GT40P heads on the 289 in my 67 stang. A fellow at the local Ford shop says they are compatible and will boost the HP quite a bit.

Anybody have experience with this particular mod? Do I need different push rods, what are some good cams for a fast but streetable car, what are some potential pitfalls?

Current engine configuration: 9:1 compression, Weiand stealth dual plane mani, Holly 600 cfm vacuum secondar; planning to put new exhaust system on. Current 289 heads are trash (long story) so I need to either do a complete rebuild on them or replace 'em.