Pay what it's worth to you! It's old it's in need of fixing and it will probably need more work than you realise, mine is a 1983 from a scrap yard and needed 10 months work and I paid £250 for it cos it's what I wanted so decide what you think it's worth WITHOUT getting loads of non informed advice (we haven't seen it) and stick to your price, if he wants more then find another one, there's loads out there and like buses 3 will come along at once when you start looking.
P.S just a quick reminder if you want to stick around it might be an idea to do an intro, not a question straight off (new members section) you will get more feedback that way, we like to have new folks onboard but it's nice if they say Hi first.