there not that hard, a few brackets and bolts and your away, im selling mine soon tho, far too heavy and gettin del sol seats, light and cumfy / supportive.
Anyway, seatbelt, i dont have any, i use harnesses, What the problem with it, if i remeber it sits too close to the seat??? i think i heated the s shape bit and bent it further out when i started, it did work but i never used it so just got rid of them. lol.