"...Are you saying these are 4X heads I have ?..."
I can't see the head numbers, in the pics. The numbers will be cast over the center exhaust ports. 4X heads were used in '73-'74, & 5C in early '75. #96 heads were used in '71, & 7K3 in '72.
"...Would these heads have the hardened seats?..."
Yes. :yes But it is said that the hardening process was improved after the 4X heads, and that the 6X heads had a better quality hardening process. I've read that because of this, some 4X heads seemed to crack between seats, more than the later 6X heads. But, there are still lots of 4X heads in service.
"...Are there hood clearance issues with Performer?..."
No. :no The Performer has about the same clearance as a stock cast iron intake. But, it's a different story with the Performer RPM. The RPM is quite a bit taller. Sometimes they can be used with the correct recessed base air cleaner. Most hood clearance issues are with the 2nd gen Birds, especially TA's. The 1st gens seem to have a little more room, above the engine.
"...I should have said I have an MSD ignition box already, and coil, so would just need the Distributor..."
I am not a fan of the MSD box, and external coil. We had a box go bad on a dirt tracker, and cost me the price of a new box. And, the self contained HEI is just so much more convenient. And it creates a less cluttered look. You don't have all the extra wires, nor the box and visible coil. If you like MSD products, you can use an MSD cap, rotor, coil, module, wires, etc, on a self contained HEI. But, it's your car. So, if you want a box and external coil, so be it. :smile22:
"...I am fine with a carb but would invest in throttle body injection, as I did my boat..."
Just curious--what will a complete FI set-up cost ?
http://www.jegs.com/i/FITech+Fuel+Injection/546/30003/10002/-1?CAWELAID=230006180003490504&CAGPSPN=pla&gclid=CjwKEAjw_7y4BRDykp3Hjqyt_y0SJACome3TBk8QZWV7xs6ncYCXl2blkjPxItP5s7YwufjIybjPShoCX6nw_wcB
Not sure, but a throttle body FI set-up might work better with a single plane intake. If you need the exhaust heat crossover, for cold weather driving, a Torker 2 intake will work. Or, if you don't need it, one of the cheap Chinese single planes will work.
http://www.summitracing.com/parts/edl-5056?seid=srese1&gclid=CjwKEAjw_7y4BRDykp3Hjqyt_y0SJACome3TlB1Qiwa-1eRbNoQPKZG4V2vZ-Si5kzqBAjrp0bp_8BoCgqrw_wcB
http://www.ebay.com/itm/Take-Off-Pontiac-326-350-389-400-421-428-455-Shootout-Intake-Manifold-Satin-/291619049853?hash=item43e5d9917d:g:L4kAAOSwFnFV95qD&vxp=mtr
A GOOD Q-jet is less than $500.
http://www.smicarburetor.com/products/sfID1/28/sfID2/9/sfID3/100
