some of you in this forum might know that i am looking for a foxbody mustang to purchase. So far I have found some really nice ones that are bone stock, but there are some that are modded and are cheaper than the stock ones. I was wondering if it was better to start off with a stock car or go buy someone's project mustang that is modded and save some money instead of buying the same parts for a stock one.

The danger in buying someone's already partly modded car is in not knowing if they had drive-it-like-you-stole-it-itis. This is a common problem when purchasing modded civics, and I would imagine that a similar risk exists when buying a modded mustang. There is also the question of whether or not the installs were done properly and the condition of the parts (if it had money put into it and is cheaper than a bone stock one I'd be wary). Overall, it is probably a safer investment to purchase a stock car rather than one that has been modded already.

Just get all the OE parts when you buy it, otherwise your gonna be screwed when it DOES break.

okay, now what about buying used parts such as upper intake, headers, cat bacs, etc?

What about them? They're used, but the only way bolt ons can break is by warping and having a leak, and that isnt really a problem.