spade lugs won't fit

That is the one thing that is very annoying about older Mac amps. I used these for a while until I finally had my tech guy remove the terminal strips on my old MC 2105 and put on modern speaker terminals. They work pretty well.
https://www.ebay.com/itm/10pcs-Gold-Plated-Copper-Spade-Banana-Fork-plug-Mcintosh-Amp-Speaker-Adapte...

My recollection is that Anticables make a nice light weight copper vintage gear sized spade
Audio Classics is a great source for all things Vintage Mac

Are you able to use bare wire?  You can get a decent connection and any oxidation can be easily cleaned off every few years.

Having previously used the (excessively) thick Naim cable previously I prefer to use Chord Odyssey silver plated or just plain oxygen free copper nowadays.

I do find unwieldy cables and plugs far more trouble than they are worth. The same goes for badly labelled input jacks!

as an aside....current Vandersteen speakers use small spades.  Richard says they sound better.

If the spade ends are built/pressed into the cable, you'll either need to butcher the cable or send it back. I use the adapters listed earlier with banana plug speaker cable ends. Has been working well for several years now.