340 Heads Recommendations- Aluminum vs Cast J

Need advice on where to go with my head situation in the Duster, been looking at posts on here Speedmaster with work or just rework the J heads and call it good, I’m just gonna be street driving and maybe a rip down the track once ina blue moon for fun, no racing.

Trying to decide money vs gain on either building up bare speedmasters or reworking my J heads, would use valve springs for my cam.

340 supposedly .30 over
915 J heads- unmolested
Crane cam 284 H12 pt# 150062
Eddy Air Gap intake
4spd w/ 3.55 suregrip
LT headers 1 5/8
Holley 4150 dbl pump
Supposedly steel crank, haven’t been able to confirm if that’s true per previous owner

Anyways, suggestions, advice, feedback welcomed, thanks dudes!

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Seems like a good setup already. Is there an issue with the heads? If you want to play then just go straight to the Trickflow. Money ahead in the long run.