I saw the video of sbc pro max head and how good the aluminium alloy is, the guides and seats. On par with Dart heads. Same thing with the BB heads? Anyone have a pair and can talk about a newer casting?

There are a few threads on these from about a year ago or so...... Just do a search

ProMaxx takes the exact same casting as Todd Marsh Sidewinder--they do nice valve job and put the name on the end--Sidewinders available from Marsh Performance are the best bet --each pair assembled with QUALITY parts to your needs and specs--he has the most experience with that head and has achieved great results porting them to amazing level--best deal for the $$ is to call Todd
They have excellent casting quality, first class guides, seats etc I think better than Edelbrocks I have used a pile of them and have been very happy for a head in that price range

I got sidewinders as well. Felt more comfortable having marsh going over my set before shipping than a big store that just puts a shipping label on a box.

Running Sidewinders from Todd with Larry Smith porting on my 440 with a F2 ProCharger with 15lbs of boost.