Oh man, it was 40 years back. Cat 390 series Diesels, as I recall, though Cummins had some big power in that range in that period was then being used for repowerings. I recall the price tag [then] of around a quarter million dollars per powerplant, and thinking that for that kind of money, some nice M48s could be put together.
We had Allison cross-drives in our M48s and M60s then, so a replacement transmission was at least a possibility, but the repowering of the radial-engined Shermans with GAF 500 HP engines from Pershings was done with the original transmission, as were the Diesel reengining of Mk50 Shermans by the Israelis and the NAPCO Sherman repower Diesel conversion, which I think used a Volvo engine, though it stuck with the Sherman tranny and final drive.
Don't know what engines of that era would fit, cooling, etc., the engine bay might need replacement, so cut the whole back end off and start over. Something like cutting the back off of a Leopard I and welding the whole thing on.
It wasn't quite that bad- the dimensions of the proposed engine had been checked, though I think some auxiliaries had to be relocated and enhanced cooling installed. The electrical system was reworked to 24 volt for cold weather starting and compatability with the then state-of-the art RT-505/ PRC 125 radios, and there was some concern as to whether the turret electrical slip ring would handle the amperages involved, so the master switch was installed in the hull at the bow gunner-radio operator's position. That crew position was considered for removal and replacement with additional ammo storage, as was done with M26/46s and M47s of the same era, but it was thought that it was worth having the additional forward-firing MG for suppression of Sagger ATGM teams, then just becoming really widespread in the Warsaw Pact armies. I don't know how a Sagger hit on a Tiger's fromtal armor would have worked out, but it seems a thing a crew wouldn't want to try.
I had the opinion the deal was very secret and that the host country was not going to be the end user, but was going to export the nicely deniable, *sterile* armor to somewhere where it wasn't expected. A couple of possibilities from the period come to mind, in at least one of which where 88mm AP, AT and HE ammunitionp wouldn't have been much of a problem.
Interestingly, the MG34S MGs aboard were to be pulled and replaced with MG42s, whether in the original 7,92 caliber or 7,62 NATO, this deponent knoweth not. But somebody obliously had infantry suppression in mind as one of the tasks for the things.
Son of a gun, you've got me looking for engineering drawings. Fun project, you should have given me a call and supplied transport back to '65!!! Too bad it was forty years ago, I wouldn't have been much use when I was 18.
I've really gone over old news news photos of the 1968-70 period and can't find any record of their having been used. And it could be that the work was never meant to be done, that it was some sort of intel operation or sting intended to bluff someone into thinking tanks were going to show up in an unexpected area of operations. But if so, those of us working on the project hadn't a clue, and we were taking it seriously. Eight Tigers, even 25 years after their war had ended, could have made a heck of a force multiplier in some places, then, and even now.