i agree with the area under lift with 30 degree but I don't think they seal as well as a 45. I would just stay with a 45. my 2 cents.

A race engine only. I’d never do that on the street.

For what it cost me to have some basic machine work done on a pair of 915s last year, I'd say it's only worth it to fix iron heads if you can do some of the work yourself.
I had the heads shaved (just a light cleanup cut), 16 bronze guide liners, 8 hardened exhaust seats, opened up for 2.14"/1.81" valves, and a 3 angle valve job. That was a little over $700.
I did the bowl porting, general port cleanup, cut the guides for positive style seals, assembled the heads w/ new valves, springs, retainers, locks. Just the parts will run you another $600+ depending on what you need.

A decent port job will be in the $1000 ballpark or so I'd say? I'm definitely no Dwayne Porter, so blending the bowls is about as much as I do. Then again, I'm not expecting 700 hp out of these heads either, lol.

Granted, a lot of aluminum heads (not all) need to be torn apart and checked out before using them, so the new cost needs that added to the bottom line.
The cheap heads have cheap parts installed in them which are a gamble.

Pontiac used a lot of 30* intake seats in their street cars way back when, so I don't view that as a "race only" thing

The last customer who insisted on original cast iron heads for his big block ended up paying a ton of money for them. He had to buy 4 sets of heads before he found a pair of castings that were in good enough shape to be rebuilt. Then the heads had be fully rebuilt with new seats, guides, valves, etc. No porting was done. All surfaces machined, decked, all threads chased, cleaned or helicoiled, etc. Well over $2000 just to get a set of good 906 heads for a resto project.

The AMC did also but I'm telling ya they don't seal to well. Some even mod the valve with a conformation groove in the valve face

Years ago I swapped a pair of decent, no magic parts or work on them ,906 heads onto my bracket car motor at that time to remove the 516 heads with 1.74 exhaust valves in them to sell them to a customer who wanted them for his build.
The bracket motor had the old TRW 11.5 to 1 compression forged (CRS Pt.#. now ) "race pistons" in it with a solid lifter camshaft, Isky rockers and so on. I didn't measure both heads combustion chambers while they were both on my bench, I was thinking the 906 heads would lower it but I didn't make sure,. Bottom line is that motor ran faster and quicker by about.200 ET and 2.+ MPH with the 906 heads on it with no other changes
My message is sale them old 516 rascal and buy a new set of better aluminum heads with bigger valves and better ports

“My message is sale them old 516 rascal and buy a new set of better aluminum heads with bigger valves and better ports up scope work twocents“

Exactly what we’re not allowed to do, rules, has to be the 1.60 ex valve, no port work. I don’t think I’ve seen an open chamber aluminum head, all closed chamber, quench is nice.
I’ll do the work so no money just time.

The 88 CC Eddy RPM heads have a CNC machine open chamber in them