Oh, if we are going for the most practical supercar for real then it depends what what you mean by supercar. Assuming something with equivalent performance to the supercar of the time then I have to nominate the Lynx Eventer
The XJS was so much better than the E-type IMHO especially with a manual gearbox and weslake heads on the HE versions - for a start it had decent suspension and brakes which the e-type lacked and it was a 70s cool car which is of course super cool.
As for the supercar I would drive every day, the Lamborghini Jarama is my number 1. Take the engine from a Countach and mount it in something more practical.
If you are in anyway interested in cars, even as an Ecomodder then you at some point want to be this guy.
EDIT - before anyone brings out stats about how a Vette would be faster - come on, you would still drive the Jarama and listen to the V12 sing as you lost the drag race battle but of course won the cool car war