[gofastwclass]

My personal opinion: potentially make him an offer on the parts you need or simply buy exactly what you want new.

The problem is you need to determine a used market value for the bits you want. If you need to pull the parts, you will need to factor your time and labour as well as part of the expense.

If the parts you require are still available new what is the cost difference of purchasing exactly what you want / need vs. acquiring these used parts that may only be close to what you want. New parts also are a known quantity, used parts are... used and potentially abused.

Finally, I'm not a fan of trying to flip stuff. As clearly evidenced by the ad you are mentioning, used speed parts for sale don't exactly fly out of people's garages without help or a bit of luck.

I'm not saying you can't potentially score a great deal, I'm just saying keep your head above water and don't get too excited on what appears to be a good deal.