Thanks y'all, and in that case I will just stay with the manifolds, also looks like first thing I am buying is springs and frame connectors
They didn't come from the factory with beefed up frame with the 429, but not a bad idea to add frame connectors if you have the budget.
For springs, without doubt, buy from
Eaton Detroit Springs, or from a vendor like NPD that sells Eaton. You can go to Eaton's website and plug in your car, but of course call it a 429. The rear spring may also need to be upgraded. Again, you can check on the website by comparing a 302 fastback to a 429 Mach 1. Stock rear springs were 138 lbs spring rate. The 302 maybe 78 lbs I think at a guess. When it come to springs, trust me, you get what you pay for.
If it were my car, I would want to seriously look at the suspension as a whole and upgrade and replace anything that is questionable. Oh boy, I love spending other peoples money!!