Q: Can one use the body of one of the EP’s for various Occasions with another proper preface? I’m pretty sure the answer is ‘no’ but I’d love to have an expert opinion.
A: The prefaces were written for each of the four versions with the intention that they would be used as a whole. There are priests who ignore that and swap out the prefaces, but I think that that damages the integrity of those prayers. I don’t know of anything that expressly prohibits or permits exchanging their prefaces, as you find very clearly with the eucharistic prayers for masses of reconciliation (where it’s allowed) or Eucharistic Prayer IV (where it’s not). I’m concluding that it’s best to leave the four versions of those prayers intact.