Solutions would be either source a better shaft or get a competent engineer to build up then grind the journal back to standard.
Using a big end shell from a different make can be difficult, it needs to match the thickess and length (measured across the shell at right angle to axis is the bolts) and the big end eye in the rod also needs to match.
The A7 shells were the ame from engine XA7 600.
Below is from the 1981 AE catalogue and gives dimensions of common bikes shells.