Hi, Sorry if this turns out to be a long question, and a non Volvo one at that.
I have a 1980 Maserati Merak SS, (mid engine) which needs new tires. The original sizes were 205/70/15 rear and 185/70/15 front. I have always used 225/60/15 rear and 205/60/15 front. I have done this mostly because there are no performance oriented tires in the original sizes and now even the latter sizes the choices are getting very thin. I guess it will be easiest to list my questions and concerns.
A). Is a passenger tire in the original sizes equal or better than the original, (1980) Stock Michelin xwx?
B). I'd rather not spend for "new" XWX's from Corker as they are very pricey and would they be as good as a modern design anyway?
I should interject that I do not race or drive too agrressively, but I do want as much handling and braking performance without comprimising the nimbleness and handling balance.
C). Is sticking with the 225/60 and 205/60 set up the best comprimise for now, it seems adequate, but I do feel that I ma leaving some handling/braking performance on the table.

D). What I would really like to do, but not sure if I am opening a can of worms is Get some wheel adapters, (stock wheels use a very odd 4 lug by 5" bolt pattern), so I can use a 16" or 17" wheel thus make it easy to upgrade to a high performance summer tire of similar overall tire hight and width. BUT, How will this change all the design in suspension geometry? The wheels will be pushed out a bit on each corner and the tire aspect ratio would go from a stock 70 series to maybe a 55 or 50 series.
I know the ride will be harsher, but I am more concerned with nimbleness, and no funky handling, (as it is the rear can snap out very abruptly at the limit...though I don't do that anymore..lol)

Any thoughts?

Thanks!