Gonna start buying parts to build my first longtail. Looking at the backh2o undoing and wanted to know of anyone could tell me the difference between the regular and the 1" extended side? And what are the pros of it or if it's needed

ive never actually seen a backwater u-joint but the extended will just give you more engagement on the shaft. Prolly not that important unless your building some thing high HP.

i have built 3 longtails, used a steering u joint for the first. the second by buddy just picked one up at the auto store and the 3rd i bought the series 12 from Boghog Mud motors. (never had a problem with any of them)