Will a ke 70 gearbox fit straight into a ke30?

Yes and no. It'll bolt in but the shifter is further back so wont go through the original KE30 shifter hole.

cut out a hole in the floor about 4-5inches back same shape as you have, find a piece of steel to techscrew in over the old hole, move centre console back or i used an auto console cut the guts out and fitted the leather boot inside it. very easy covered heaps in build forums

Ok thanks guys I was just wondering as I have 2 ke 70 boxes at home I thought I could use them I case of something goes wrong with mine