5M head onto 7M block
 

I gather this can be done but cant find any info on it, has anyone done it?

Yes! Yes it can be done... However you will need to find certian parts for it to work..You will basicly have a 6MGE then..You will have to pull the pistons and put in some out of a 5M..Then you will have to have the crank pulley and harmonic balancer off a 6M to make up for the stroke increase.. So long story short just buy a 6M or just upgrade to a 7M altogether..Yes you would have to also swap the harness and ect.on the 7M... The 6M will use the stock external everything from the motor including the ECU and harness only the short block changes..