Need advice on purchasing this CB750

Hey guys - I'm in the process of negotiating a 78 CB750 (see attached album for pictures). Cosmetically, the bike is in great shape. It was professionally retrofitted 3 years ago by a reputable bike shop to give it the look you now see. However, they didn't touch the engine. The guy I'm talking to is the 3rd owner and bought it from another guy shortly after it was outfitted with the new look. He said it wasn't running well when he bought it so he fixed the compression, timing, carb adjustments and wiring updated.  Also added a top end gasket kit to improve performance at higher speeds.It has a clean title. I haven't test drove the bike yet, but did hear it idle and it sounds great. No misfires or anything. It needs new front fork seals, speedometer doesn't work, true mileage is unknown, battery is dead and I'm probably going to find out it's not charging properly. So my question is - what's your impression and what do you think a fair price is for a bike like this? He said it has $8k invested which seems exaggerated to me and I think I can probably get it for under $4k.Here are a few pictures. The first two are current. The last one is right after the cosmetic overhaul a few years ago. Appreciate any advice/tips you guys can provide.https://imgur.com/a/dpFEjS1 via /r/CafeRacers https://www.reddit.com/r/CafeRacers/comments/bgi2py/need_advice_on_purchasing_this_cb750/?utm_source=ifttt