I look forward to seeing this build. As for using the Dyno Don Comet, it might be an option but unless you go to the auction site, it seems hard to find.
Actually a bit of correction. The McLaren was originally issued by AMT. The only three MPC Indy cars were the Dan Gurney Eagle, also issued as a Bobby Unser car, Lotus Indy Turbine and 1/20 Silent Sam turbine.
A couple of comments. Of the later rear engined cars of the early 70's, the Monogram version was one of the nicer ones although it does show the 1/24 scale size difference over the other kits manufacturer's 1/25th offerings. I've got several of the first issue Swamp Rat XXX's. I hope the decals are better than the Revell offerings.
The all white box version has value. The one with the yellow stripe is worth about a new kit in today's prices. Here's the question you need to answer. Would you get more pleasure building this or something else? If more pleasure, build it in the way that will give you the most enjoyment. Here's some info on the original: https://www.facebook.com/watch/?v=682143476370365