Question - seam welding a CSA GrpIV Replica

[toscana]

Hello

I am starting a CSA GrpIV replica car for vintage racing in the States.  I begin with a plain production 124, not a CSA.

I understand seam welding the chassis for strength is necessary.  What is the full extent this needs to be done?  Can anyone provide critial areas?  I have some pictures from this site and bits of information. 

Also, is there other chassis strengthening that I should consider while the shell is completely media blasted and stripped?   

I would be thankful for any guidance, a listing of areas or pictures from someone with specific knowledge.

Thanks for any information you can provide.

Regards,
Don Tuscany
Wisconsin, USA