ancosta --
my guess would be that car would sell for about $7k or $8k depending on the level of detail and accuracy of the restoration. small touches like the style of steering wheel, correctness of seat covers, level of body work could push the price higher. a concours quality MGB with 90% original parts and low, documented mile MIGHT get you in the $10k range.
as for speed, there are several options. the best, im my opinion, would be to update the internals to modern, lead-free specs. blueprint the engine and possibly add a fast road cam. with the proper exhaust and tuning, you'll at least FEEL like you're going fast. (stock 0-60 on these cars was around 10-11 seconds) there is a company in Australia that makes a roots-type supercharger for the MGB with wheel horsepower measured between 140 and 170 HP depending on the level of detail put into the engine rebuild. and they require blueprinting before warrantying the unit. vintage Judson superchargers can also be found, but are hard to maintain and wear out quickly. but there are cars with V8 conversions, V6 conversions, turbo Cossie conversions, Miata conversions, etc... you name it, you can do it with an MGB.
EDIT: The craziest conversion i have seen published.
[img]http://images.snapfish.com/3349%3B89923232%7Ffp37%3Dot%3E2326%3D565%3D3%3A7%3Dxroqdf%3E23232%3C2%3C%3A3987ot1lsi[/img]
[img]http://images.snapfish.com/3349%3B89923232%7Ffp34%3Dot%3E2326%3D565%3D3%3A7%3Dxroqdf%3E23232%3C2%3C%3A3988ot1lsi[/img]
