Hi,I'm the guy that did the '67 conversion. Actually it was the whole chassis from a '95 t-bird. It is all heavily modified and as much of it as possible is blended to or hidden by 67 mustang panels,or just customised. The fenders are mounted on custom made fender aprons,a very ingenious way of doing it is all my buddies creation. Even my body guy with 30 years of custom work was impressed by the simplicity.
Anyway the 4v will fit those years. Before '67 the entire shock towers have to come out,and a mustang II type suspension is best. '67 & '68 I believe just the lower portion has to be trimmed,and I'm not sure if you can still use the stock suspension. But you can go with a mustang II or fatman fabrications has a set up that uses a coilover struts with SN95 suspension and braking upgrades. A call to DVS restoration will answer any questions.