A buddy is having a 525 short block freshened and bolting a set of Dart 308 steel heads on. My question is, how much of a difference in performance is there between using a 525 intake vs using a 502mag intake manifold? Thoughts on this?

The Mag Intake Manifold is VERY restrictive and you'll run out of power about 5200 rpm unless they're heavily modified.

Last year I built a set of engines and cut down the runners and was able to get power to run out to 5300-5400 but even then it choked it. The engines would have made a lot more power with either the 525 or single plane intake. They came in around 540hp/560ft lbs, but they would have been an easy 600hp.

Some pics of the intake in my album from the build here; http://s706.photobucket.com/user/Fun...onys%20Engines

I dont think you'd see much difference........Agree with Panther.... both intake, TB and fuel system are restrictive, Im building 525 long blocks with Vic Jr. single plane intakes and 930 cfm carbs

Kreed.... Had the 502 MPIs on the 540s with the same heads, asthmatic dogs
Put some Victor JRs, QF 850s, 525 EFI cams in there and have fun (make sure he checks valve guide clearance)

Both are equally junk when comes to making power above 5500