The real problem with ZF is input shaft vs output shaft height is about 3", ZFQ is slightly better with its small amount of hypoid & T44 has about 1.75". It doesn't really effect SBF as originals ran very small flywheel, MKII with FE has large flywheel which is a major problem in your road going scenario, Ive got around that with offset reduction starter & 289 ring gear dia for my FE.