Yes, you have to completely remove the drivers seat and install 2 cross bar supports. As well as a plate underneath the truck. The kit comes with everything you need, grade 8 nuts and bolts. As well as passenger / battery box hardware as well. The back seats are extra, you'll have to take the bases out and possibly redrill holes, we use large washers for better support. Hope this answers your question.
Been buying and selling the H1/HMMWV since 1995 over 600 units bought/built and sold.