Got $15k to put on my build, where to spend?

[ncsurveyor]

I’ve got a 68 C10s i recently bought. I’ve been driving it daily and it runs great but I’m wanting to make it more reliable/cool/restored. Where do I put the money? Do I splurge on the motor and trans? Maybe an ls3 or lt1? Or should I stay simple and do an ls1 or 5.3 and spread the money out over other parts? I’d like to update the suspension, drop it with disks and new wheels. I know $15k won’t get me too far, just trying to decide whether to go big on the motor or not....