small block heads for a long distance cruiser

LA-X has been out of production for at least a year; IIRC the foundry went out of biz and no one has gotten new castings restarted. All you can get are MA-X and the EQ equivalents. ah bin keepin' an eye on this awl.....

LD cruiser? Does not need max flow. RPM's would be absolutely fine. Or the stock larger heads...308's? I'd personally go with the RPM's as they flow decently OOTB.

I am with AJ on the economy aspects. Go with decently high CR and a modest quicker ramp cam (like the Howard's optimized for the larger lifter). With the OD, low 20's is for real: I used to get 18.5-19 mpg at 65 mph from a 351C, standard 3 speed C4, and a 3.08 rear axle. But would beat stock 440 GTX's all day long and was a very good cornering car with Bilsteins and the right tires. Went for good breathing (351C heads and single plane by golly), headers, and yet a smallish, torque orienated cam to aid the fuel mileage. 10.3 SCR, 8.3 DCR. (No Voodoo-type grinds available in those days.....)

So that is your formula IMHO: good breathing, 9.5-10 SCR, mild cam and DCR around 8. Did a 340 'Cuda with my son with the RPM's, Spitfire shorty headers, Performer intake, and 10.0 SCR and 8.0 DCR. So it is built just like that, but used a 268-ish cam and fuel mileage is only around 16 mpg, with a 3.55 rear and .83 OD. But boy does it hammer out of the corners in the mountains here in 2nd! Throw the car hard into the corner and hammer down with confidence that it will hook up and you can power steer through and nail the gas at exit and be GONE! Sorry, I got carried away LOL. Too much fun.....