so I assume this is a 2 bolt block??? Of course, you have probable already identified the rear cap---

If you take a magnifying glass you may be able to pict up marks for 1,2,3,4 on the caps but if they are there they will probably be very lightly stamped---other than that its the switeroo method, try, tighten, feel with finger, measure with dial bore guage--

Of course you can take it to a shop for alighn hone and let them figure it out