I think you have made the right decision to not buy that rib. Although I hope you offered to pay the ebayer his listing fees :sick
That pair of old coal burners on the back is one good reason to run in the opposite direction I reckon you would be using about 2 litres per mile at any reasonable cruising speed and I very much doubt you would see more than 35 knots out of it.
For 6k there is better to be had IMHO, just bide your time.
Four year ago I bought Keymar (renamed Danny Boy) off this website if you do some searches you will see what a good boat it was. Osprey Viper 5.25 with an immaculate 90 Johnson 90HP on the back. I paid about 5k for that boat, granted they dont come up like this every day however they do from time to time. I will keep my eyes pealed for you