65, the .040 oberbore is fine, no problem there, I wouldn't even consider aluminum heads, especially with a Performer intake and iron exhausts. Almost all of the available aluminum heads have chambers too large for a 289, and the better breathing ability is wasted, or at least unable to be utilized, if you're choking the engine with a Performer intake and cast iron exhausts. Yes, you should get another intake, and no, you won't lose low speed power or economy with an RPM or a Stealth 8020, the performer is that bad. If you want a better intake, and you think the RPM or 8020 is too much, you might like a Weiand Warrior 8124, a dual plane that is lower and smaller runner volume than an 8020, but taller than the Performer. I wouldn't get a pair of aluminum heads and then expect them to happily seal against an iron exhaust manifold.
Yes, your iron heads can be improved, but be carefull what is done and who does it. 40 years ago, one used to use Chevy valves, but they are too short, and you have to mess with springs and pushrods while you are in there, because they Chevy valves give too short of an assembled height. If you go to a shop and ask for Chevy valves, you could end up with a 1.84/1.50 combo that leaves you needing a lot of new parts. You should specify that you want, if you are using rockers WITHOUT rail tips, 1.94 intakes, 5.010 long, part #01-1002.100-8 and 1.6exhausts, 5.010 long, part #01-1001.100-8 & for exhaust seats you need SBI SB1625-1 seats. You'll want 35-305V stem seals. If you open the bowls and smooth out the cast iron 'boogers', that will be plenty. Be exceptionally carefull on the shortside radius, you only want to smooth the casting flash, not remove material or change the shape. The small chamber C5AE heads are a great head for a 289 ! LSG
Appreciate how feedback keeps coming on this thread! I will say, though, this is why it gets frustrating - have multiple people tell me that the Performer is not only fine, but probably the right solution, then one very strong opinion telling me it's garbage and that it should be replaced (which was my original plan). Bottom line, I probably just need to make a decision and stick with it, as it seems none of the options are "fatal". Again, I'm not trying to squeeze every bit of power, just improve where I can easily.
In terms of the heads, I think there was some confusion - I am not upgrading the valves at this time. Given that the heads were rebuilt with new stock-size valves just 10,000 miles ago, I am going to keep everything as is, put the roller rockers back in,
and have the intake and exhaust ports cleaned up. One thing the head guy did recommend is a sort of back cut or bevel on the valves, as he stated it allows air to flow better and it's something he does on all his heads. I don't know anything about this, but given the guy's reputation I figure he must know what he's talking about. I did tell him over and over that this is a street motor that I just want cleaned up, and he seemed to get it. He sent me some pics of 289/302 heads that he's worked on, which I've attached. Thoughts?
Sorry for the pictures being sideways. I fought for 15 minutes trying to get them to post right side up, even changing the orientation of the original photos, and nothing worked. So I guess it's a forum problem.