[chumbucket]

Welcome to the site chesapeake. First of all, I'd like to say, good taste in boats. ;D (I own both a V20, and a project F233).
For some thoughts on the Wellcraft;
1. For $3000, if everything is in working order, you probably can't go too wrong. You might want to try even a bit lower.
2. You said the motor was in good running condition. Did you sea-trial it, or just run with the ear muffs? I wouldn't make a decision based solely on running with the muffs. Do a compression check, sea-trial, check lower unit grease for signs of water intrusion, and check the oil injection system if so equipped.
3. Yes, the transoms are curved outwards a bit.
4. The lip around the motorwell cutout is standard. A plate behing the motor mount is not. I'm not implying that the transom is bad. Previous owners may have placed that there when repowering to cover holes from original motor which may have been different configuration.
5. Yes, V20's of that vintage were open under the caps. If you look through several of the site members gallery postings with boats also of that vintage, some have closed them in and done a very nice job at it.
6. I believe any and all deck water drains into the bilge on that vintage boat. They were not self-bailing. Make sure you have a good reliable bilge pump.
7. On a final observation, I'm not sure what brand of trailer is under the boat, but it looks to be a lesser popular model which would make repairs (ie, locating parts) difficult. Just something to consider.

Overall, I'd say for the right price, not too bad. Offer him $2500 and see what he says. Worst that could happen is, he says no, then go from there. Don't rush into anything. If and when you're ready, think about it for another day (???). I've made a few impulsive boat purchases in the past myself :-[

Whatever you decide, best of luck. ;) ;D