The Shocks don`t hold the car up ,,,& have absolutely no bareing on the "ride height" of the car,,,you`d best fit a set of """HI-LOS""",,,adjustable alloy cones,,,these will enable you to set the ride height where you want it to sit.
& yeah,,,as Greg said,,,a major portion of what i was saying about 13" wheels compared to 10" wheels is to do with the un-sprung weight,,,very hard to find a 13" wheel/tyre combo as light as you can get, to come anywhere near the weight of a very light weight 10" wheel/tyre combo & yeah, split race 13" wheels & canvas tyres are very light,,,but simply not as light as split 10" race wheels with canvas bags

simple as that...
However,,,another very important issue plays with you here too,,, a change in suspension geometry comes into play once 13" wheels are fitted & you then try to lower the car back down to a reasonable height, all your control arm angles go out the window
i overcame all that on the "New Blew" car with the re-positioning of all the front control arms & severly shortened (made em myself) Hi-Los assys & a big change in the subframe tower top & lower rear frame tongue heights & also re-positioning of the bump stop brakets & also a raised re-bound rubber pillar,,,big job to do properly & works awsomely!!!!!!!!!! But, i won`t bother doing it again...just too much work with very little gain from a good 10" wheel set up.
also you have a very large wind resistance issue with super wide wheels & flares,,,you all may not think that it`s much of a problem, but i don`t believe many of you have ever sat at over 130mph in a mini for any amount of time...normally a mini hits a wall of wind at about 80mph & the average 1275 or bigger donk will pull through that no problem to about 100mph,,,but to try to get to 130mph & actually hold it there for any length of time takes a very good donk ,a well set up suspension & a driver with big go-nads.
i`m now goping back to 10" because of all those issues,,,maybe i`m just getting lazy in my old age
be on the look out for a citric acid green fastback mini monaco , on 10" wheels with 180hp twin cam turbo power in the near future

my new road mini.
yeah!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!