It may not be completely relevant because of the timeframe, but I have two datapoints to offer on this question. I bought a built 3.4L from a local racer who had totalled his 914 at Laguna Seca about 10 years ago. It had been built on a 3.2 case w/ Mahle P&Cs, Carillo rods, PMO 50s, and a special Web Cam grind, but no exhaust (since it was from a 914 and I was putting it into a 911). It had 3 races on it, made 256 RWHP on a DynoJet, and I paid $7500 for it at the time.

A few years later, I bought a '74 911 that had an engine very similar to the one you are considering--a recently rebuilt 3.4 using a 3.2 Carrera base, EBS replated 3.4 jugs and JE 10.3:1 pistons, 964 cams, with stock Carrera induction and a performance chip. This was a complete car, running and driving, not just the engine, and while the tub had some rust, I paid $8K for the whole package. It made 206 RWHP on a Dyno Dynamics machine with open pipes.

Adjust these datapoints for the change in value of the USD and the market over the last 10 years, and hopefully you may have some additional clues about the value of what you're looking at.

HTH,
TT

Tom - that's very interesting data. Thank you.