The ports on Gen 6 "Vortec" 7.4L heads are oval. Any oval-port head should bolt up.
MOST oval-port heads will have far larger combustion chambers that therefore drop compression ratio. Edelbrock (and perhaps others) have aftermarket oval-port heads with the same approximate size chamber, perhaps with larger valves. They're not cheap.
The problems with the Vortec 7.4L heads are that they're modeled on the previous-generation small-block (TBI) swirl-port heads, among other problems. There's a bigass ski-jump cast into the intake port, and just like the small-block swirl-port heads, they're turds for higher-RPM performance.
They've also got non-adjustable rocker studs using a smaller threaded hole for the rocker arm stud. Depending on the cam you choose, you may have to--or want to--convert to an adjustable rocker system.
Mine had valve rotators under both the intake and the exhaust valve springs. You'll want to scrap the rotators in favor of .300 thick valve rotator eliminator shims, and there's at least two part numbers depending on which valve springs you install. I needed 16 of 'em, not the usual eight. And you have to watch how the shims fit on the intake valve guides, 'cause GM isn't too picky about the radius at the base of the guide boss where it transitions to the spring pocket. The shims got hung up on some (not all) of the intake valve guide bosses and didn't sit flat on the spring pocket.
I thought the 7.4L Vortec heads were a "factory performance" deal like the small-block heads are. Nope.
