Lets start with the questions below. You're asking questions that can get quite blurry on where the line is.
1) What CP3 is in the truck currently?
2) How do you use the truck? IE do you tow, is it a toy, is it a work truck etc.
Personally I would think if you have 100% inj, 65mm, and the OEM CP3 still keeps up you're maybe low 600s which is less than that 65mm turbo is capable of. If you upgraded to a 72mm you will be quite under fueled for what that turbo can support at that point. If it were my truck with the mods you have and an OEM CP3 the first thing I would do is upgrade to a 10mm or 12mm to help support what the rest of the system can do with a 72mm/100% inj.
As for the engine build there are MANY ways to skin that cat like overall HP goal etc. For a budget/1k "safe" build using something like a Callies Durastar, SoCal/DHD/Wagler budget rods, Mahle motorsport or Fingers cast piston, ARP hardware throughout etc is a solid choice.