I am all with Arthuy on this.
It is a totaly different case than replacing a sill / footwell / boot floor / inner wing etc.
Suspension and steering is relying on the bulkhead for strength and accuracy. The shapes there are complicated, the metal thickness varies for a reason, and even if you could just graft in the whole area, you will need jigs to be sure that everything would fall in the right place.
I am not saying this to underestimate your competence and restoration skills, i just feel that it is a case that you'd better avoid.