The first engine rebuild I ever did was my old TR4a, I did put the connecting rods on the wrong way. When I went to put it back together I noticed the offset, which I had not made note of on dissassemly. None of my manuals helped, there was no internet. I guessed and put them on wrong. If you try to spin the engine by hand you will figure the problem out pretty quickly.....it won't make a full revolution without the rods hitting the block.
It was corrected before any damage was done.