Why I'm working with Gessford is to guarentee I'll not only get the right parts, correctly modified if required, but also matching components throughout. It's like working with your engine builder and LISTENING to his expertise as opposed to buying stuff from Jegs, Summit or e-bay. The additional cost factor (IF any) is a good investment. I would say to all it is a GOOD plan to single source your parts for such a project, wether it be KC or Southern or who ever you feel comfortable working with. Trying to save a dollar by 'shoping around' may cost you down the road!
Or would you rather take the expertise they offer and then blow them off and buy your parts from another source? I don't work like that!