You can use your stock harneess if you change some plugs, google it there is alot of info about if to do it yourself. If you run the h2b kit you will not need h series mounts you can you use all stock mounts b series mounts with it. There is some machine work that is needed on the crank pulley or some frame beating on the drivers side to fit the h series in there with the h2b. If you decide to go that way,and also you have to shave the back of the block a little for the axle to rotate without hitting it. Also the hood will have to be brought up a little with spacers to clear the intake manifold with the kit. Also you will need a aluminum flywheel the stock flywheel will not work with the the h2b. One more thing you will also need to remove the backside balancer shaft pulley to clear the drivers side frame rail. Seems like alot of work but in the end you will love the feel of a b series tranny over the h gearbox. I would recomend getting a shorter geared tranny the ls tranny is not the best if you are going to stay all motor with this setup. Lsd would be nice also.