Broken Head stud - change the head while I'm at it?

[FricFrac]

I have an '83 280ZX with a P79/F54. The rear exhaust stud is broken off below flush on the head. I'm going to pull the intake and manifold off and replace the exhaust (Ceramic coated header and 2.5" aluminiumized exhaust from MSA) while I've got it pulled apart.

 

I have another p79/F54 in the garage and I have an E31 a friend is selling that has a cam/springs/valve job. He's getting the specs for me but I don't have those right now. If the E31 head has the bigger valves would that be a better option on a stock EFI 280ZX or should I throw the P79 from the other engine in our just get the stud removed from the P79 on the car?

 

My main concern on the E31 is that the P79 has a head temp sensor and I don't believe the E31 has the sensor. Will this cause an issue with the stock EFI? Does it care if the sensor is hooked up or do people just leave it dangling? If its dangling will the EFI try to run in "cold" mode and if so does it affect performance?

 

Also if the cam is mild will it be OK to run with a stock EFI/performance exhaust? I know the EFI doesn't like an agressive cam but there isn't much info on a mild cam. Any idea of what the spec range on a mild cam that would work with the stock EFI would be (yes I've searched)?

 

I know the stock EFI doesn't like an agressive cam but is there an issue with the raised compression from using the E31 with the stock EFI?

 

Can I get around any EFI issues from a cam/higher CR that a E31 swap would cause by using an Z31 NA ECU?

 

I've spent hours searching this and other forums regarding this swap and most of my other questions have been answered but the above was the remaining questions I couldn't find answers for.