Do a close inspection of pushrod to rocker to valve tip geometry.Mine were way off.Had to modify guide plates to correct.I believe another auminum head big name also mentions this and to use their plates for correct geometry.As for my experience so far,i've had good luck.I have nothing to compare to though because i assembled with these heads.As far as reliability,1 1/2 years of street driving with some 1/8 mile drag racing and no problems-----so far.As for performance,my car is a 67 chevelle street car,461 cubes,4000 converter,turbo 350,4.10 gears,3 inch exhaust,single plane intake,950 proform carb,255/607/108 bullet solid lift cam,10.5-1 compression and with 28x9 slicks it runs 7.00s@98mph with a 1.56 60 ft. time.Hope that helps.
You have a very similar setup to what I have.... I was hoping for some 6.8 or so out of mine so it looks like I will be in the ball park. Mine is a 468 with the Pro Comp 320 heads, Manley valves and Isky springs, 10.5:1 speed pro pistons, Crower 252/262 @.050 .607/.620 lift on a 108CL, Holley strip Dominator intake, Holley 850DP, TH400 with a 4500 nitrous converter, 4:10 gears and 29.5X10.5 slicks. I also have a 275 shot on top just to move things along...lol.
As for any problems with the heads on assembley I have had no problems at all. I bought them assembled (minus the rocker studs and guide plates which I just used the ones out of my stock heads). The only 2 things I have had any issues with is getting the correct head studs for the heads and custom pushrods. Not that either is any big deal they are just differant than normal. When I ordered the head studs I was told that they were for these heads and they had 4 differant length studs. I needed the set that had only 3 differant lengths. So I ended up using 4 of my old head studs and all is well. As for the pushrods the long ones are your standard +.100 pushrod (9.350) but the short ones came out to be +.270 (8.550) But you can get them from Trickflow at a reasonable price. Other than that everything has gone well with the assembly. I have not encountered any of the "horror" stories that you keep seeing around. I know already that they do not flow anywhere near what they advertise but that is no big suprise. From the flow numbers I have found from reputable machine shops that have posted them they actually flow around 330 on the intake and 230 on the exhaust which is not bad at all. Pluse you lose and extra 100 pounds off the front of the car which is never a bad thing.
Hear are a few pics of my heads and them on the motor.
On a side note I am runing an oval port intake with these heads. I tried cheap felpro oval port intake gasket on them and the port stuck out over the top of the gasket but with an Ultra seal large oval port intake gasket it all works nicley. My intake is also ported to that intake gasket so it all works out well. You can see in one of the pics how the ports line up.
Sorry for such a long post but I thought I would give a little detail since I never could find and worthwhile info when I was searching for information on these heads.