Zhead, I'm still about, LS1 due for its first (of many ) installations over the next couple of weeks. Need to pop up to get that rad from you at some point. Sunshine and a taxed 260Z plus other stuff put pay to me ripping the engine out sooner; however, tax is up at the end of the month so.....
Reading through this thread has kept me amused for many days.
For my shillings-worth (beware potentially contentious comment following) I would say that there is realistically very little difference between a second-hand TVR and Hybrid Z, £ for £ you could get both to do exactly the same for approximately the same amount of money. Of course if you did some or all of the work on a standard Z yourself, it would be substantially cheaper and, if this is your bag, entirely different and personal i.e. suited to your tastes/requirements for a car!
My car, a 570Z if you will, will have a modified LS1 + 6 speed, Quaife dif, Arizona Z Suspension, Brakes and Control arms, various bits of body strenghting with roll cage plus a few other niceties (elec windows, Remote locking, etc). Budget £13k. Expected power 450bhp, with total turn key reliability, comfort and fair 26+mpg. In real time I would expect this car to at the very least be on par with a 5L Chimaera given driver equality.
I have looked to build a V8Z for many years because I love the feel and amusement of manual V8 cars and I love the look of 240/260Z's (plus I can fit in them which is more than I can say for TVR's, ahem!)
If you like the look and enjoy the ride of a car, buy it and drive it!
If you can't find all your favourites in one car, build it!
Zbirdy, I'd say, drive the car, if it puts a smile on your face like you swallowed a coat hanger then buy it! Provided you get it looked over by someone who knows their TVR's, then you pays your money and takes your chance like anyone else buying a second-hand car.
Hope all goes well.
Steve