Something like 1.75 million Mk1s were built between '59 and '67 (including the variants like vans, woodies, pick ups etc) and I'd imagine a vast number of them were modified / souped up in period so I don't see any problem with going down that same route fifty years later. It's your car and it doesn't really matter what anyone else thinks, and as has been said you can easily put it back to standard spec if the need arises.
Best of luck whatever you decide to do!
Edited by WMU 211G, 28 September 2015 - 04:08 PM.