Given your TVR heritage a V8 is the only option. I have driven 175k miles in a 1980 +8 with a John Eales 3.9L. 50k miles before that with 3.5L. 3.9 is superb, 3.5 was still fine. If you are using it for weekends and the odd trip who cares about fuel consumption. As others have stated it's down to personal preference. If you are thinking pre-cat then cars are 30+ years old, pay really good attention to the condition of the chassis and woodwork.
Stephen
