no mate the Capri box has a longer main shaft so will not fit you can either use a sierra 5 speed type 9 or the standard 4 speed you have but the gearing is a bit bad you should be able to pick up a gear box 5 speed quaife for about £650 you will need to get a alloy RS bell housing but like we said before it does involve moving the gear stick hole and mounting back so look for a 4 speed quiafe to make life a bit quicker and easier for you.

As far as 2.8 rear axle goes you will need to get a RS prop with atlas rear flange on it try WWRS they will have one in stock but it does mean more welding and also a set of arches as they are much wider than the axle you have now. Your best bet would be a atlas shaft conversion with a 4.4:1 diff with lsd and a 4 speed box it all depends on what the car is going to do?