Can I leak any place else?

O K so here I go with my first post. I picked up a so called rebuilt 200 for my wifes 64 1/2 mustang. The block number is a d8be (78 200 if I understand the number sysstem.) that was only rebuilt 15,000 miles ago. Well after much work on the engine bay and under the car I have installed the motor and trany that was attached to the block (c4 auto) and set up the rear with the right pinon yoke to accecept the drive line for the c4 (since it was a 3 speed manual before). Here are the problems I have since the start up. The rear main leaks, the c4 leaks, the rear end leaks and to top it off the head seems to leak between the block and the head. WTH. OK, i can deal wit the rear main, and the trans, but I put a new seal in the rearend, and as far as the head, its just a faint amount . Do I need to be concerned or is this normal for this year of block. Please help, thanks Idastang