Wow, this is an easy answer for a car. Tube chassis Countach Kit car with a twin turbo destroked billet lower end small block.
Machines.... a truely BLANK check.
I would call the riggers and have them come get my EXCELLO mill and have it taken to a rebuilder and tell them to do their thing.
I would then locate a Colchester with a 15 inch swing and 60 inch table and do the same with it. Ship directly to a rebuilder and then to me.
I would also get a surface grinder.... B&S most likely but a bigger one. I can't fit a 618 in my shop right now. I would hunt a big one down though, full rebuild of course.
I would also search out a shaper.... not sure what... haven't got that far yet. But something Cincinnati built, keeping the rebuilders busy.
Lastly, a Hardinge HLV-H. I can't think of a better lathe made for accuracy.
Maybe a matching CNC Hardinge..
May also locate a bigger Monarch. Nothing crazy, 20 inch swing max and 80 or 120 max length. that one would be the big bill form the rigger and rebuilder.
I would find a CNC mill also at some point... and go over to the tech school to learn CNC machining.
But with a blank check I would go 5 axis, multi spindle crazy stuff. Honestly this is the purchase I would question the validity of even more so than the bigger lathe. It would probably end up being a Hurco VM5i or something simpler like that. It's reasonably all I would ever really need.
Welders.
Figuring I am shooting for the moon here.
New Lincoln top line TIG machine with a cooler and all the bells and whistles.
New Lincoln MIG, same deal.
Two plasma cutters... one 50-60 amp. Lincoln. Yes I like the red ones.
The other a big dog, with a 5 by 10 CNC table. Water jets are neat, but very expensive to maintain.
And of course the obligatory call to KBC or some tool vendor.
Most of their kits. end mills, reamers, drill bits, grinding wheels, boring head sets and the like. All the machines in the world are no thing without tooling.
Then the call to the steel vendor. I would say 3 truck load of various material. Got to have stock to work with. And enough extra stock to build stock racks, welding tables machinery bases.
Lastly, a nice big granite surface plate and proper meterology equipment for it.
Oh, now I am editing.... forgot stuff
Parts for a heat treat oven. I would rather build it.
While on the high heat topic. materials to build a forge. couple anvils and a collection of blacksmithing tools. And a power hammer for when I am being lazy and when I am too old to beat steel and form it by my own hand.
The last and most important thing. A reasonable guest house for my son so he can share in the joy of the shop.