McIntosh Double Box?

Usually their equipment bolts to an inner rigid bottom piece that fits inside the inner box, that is the primary method of preventing movement.

KEEP that outer box, McIntosh would never ship it without it, and UPS REQUIRES Double Boxing for any insurance claim.

You could cut the outer box, flatten it, then if ever needed, tape the heck out of it.

If you want, sell it, or toss it, or ask a friend with space to keep it for you. Invite them to visit you, bring the damn box!

Or, in the future, McIntosh will make and sell you an outer box, and ship it to you, for $____. I paid $75. for a box I bought many years ago.

Another possible solution is only use the inner box for the equipment & then put other things you’re bringing in the car in the outer box assuming both boxes can fit by making room for it with the stuff you put inside it. 

Absolutely keep ALL original packaging. FWIW go the Pirate ship and put in the large box dimensions and total weight, look at the pricing with insurance. If you’re driving cross country are you stopping at hotels? Have to unload it every night ? Last year I purchased a couple shipping cartons for my amps. The boxes, packaging and postage to my house was almost $400. Food for thought and congratulations on the Mac. Cheers , Mike B. 

I have bought and sold a lot of McIntosh equipment. Have never bought anything without the original packaging nor sold without it. Do whatever it takes but keep that packaging. I live in a town in S.W. Oregon with a population of 600 and keep every box for everything. Sooner or later it always seems to pay off. Enjoy that preamp it is a gem.

Yup...keep everything!  Damn squirrels ate my box for my C220, and I had to buy a new double box to ship it in.  Not cheap!!