How much chassis stiffening needed?

Well, finally got the word from the machine shop that my 440 block is good to go!
Dropping a built 440 into my 1969 Slant 6 Dart.

Question: I figure on making around 550HP with this engine (maybe a 150hp shot of nitro down the road). Would just welding in subframe connectors be enough for the chassis to handle the power or would I need more?
*This will be mainly street driven tire burner but I intend to participate in events like Drag Week as well.
Thanks.