Marcos Maniacs

I'm trying to source tires for my 1600 GT.

Originals are 185-70x13.
Dia. 23.2", Section 7.4", Tread about 5.5", Rim width 5.5

Bad news is that this tire size appears to only be available with low HR speed ratings, and 
from ONE company.

So I'm thinking of using a 185/60x13 instead.
Dia. 21.8", Section 7.3", Tread unlisted, Rim width 5.5
These appear to only be available from Sumitomo, in an HR rating.

The lack of choices has me considering a change in rim diameter. 
I have to buy new wheels in any case, but don't want to have to buy another set in just a 
couple of years if useable 13" tires become totally obsolete.

It looks like I might be able to run 195-50x15 tires.
I'm hoping that 15" rims would still look traditional, without the Conestoga Wagon Rim 
appearance that is so revolting to me.
The 195-50's are available in "ZR" rating's, and there is a very good selection.

Anyone know of more/better 13" tires that are currently available?
Anyone used the Sumitomo tires?
Anyone tried 195-50x15's?

The rims will be a lot more expensive than the tires, any feed-back would be appreciated.