I wouldn't call them cheap and nasty, but only because they are not that cheap. You'll get a car that will turn heads wherever you drive but only because people are pointing and laughing.
The MR2->F40 conversions I've seen look awful. The proportions are all wrong.
The MR2->F355 looks better, although I notice that on the website none of the pics have anything to give a sence of scale. In the real world it will look 7/8th scale at best. I'd question the prices. Just shy of £10K for donor car and kit, but that's un-fitted and un-painted. Don't know how much work is involved but add a couple of grand for professional fitting and a re-spray, plus another £1500 for a re-trim and you're looking at maybe £15K+. Whatever it looks like outside it's still worn out MR2 running gear, unless you want to re-build the suspension and modify the engine, in which case that's more to add to the budget. Don't expect to much of that back when you come to re-sell it.
You could go for a cheaper kit and do much of the work yourself but chances are you'll end up with plastic padding and rattle can special, which will look worse.
The
406->F360 kit is even more expensive. There's no price on the finished car for sale on that site but I'm told the owner is looking for £28K. That's a stupid amount of money for something that is still going to drive and handle like a Peugeot.
Given that sort of money to spend a rusty old MR2 would be last on my list.