14 BFF WMS-WMS widths

[NickontheHill]

Ok so I have read a lot about the various widths of the 14 bolt FF but I haven't seen any indication about the suitability of them for use in, say, a 1971 K20. Between the 63.5" width and the 67" width. Is either more suitable or unusable when replacing an eaton HO52?
I am about to purchase a 14bff out of an '85 k20 that was a cab and chassis truck. It measures 63.5". I will be running stock rims with no intention of ever going bigger than 33".