This topic came up on another website but I think the consensus was very little of the "Stress Crack" issue had been observed by the respondents. I for one have reviewed more tri-five chassis than I can count and NEVER found one to display the condition. Others that answered seemed to follow suit. Now don't get me wrong, I am certain some have seen the condition however I just don't think it is as prevalent as those on TV selling an aftermarket chassis may elude to. Some however may in their efforts attempt to push statistics to make their case. Just remember, in 1955 alone, over 1.7 million of these cars were produced so any claims of having observed a quantity of these, say 10 – well that’s only .00058% so don’t run and find a cliff to jump off of.
I would however be remiss if I didn’t at least say this; If you have the funds and an aftermarket chassis is in your plan, then by all means become educated prior to purchasing. Some out there lay claims of being the strongest on the planet. Some are crafted from 2x4 rectangular tubing. Some use a mandrel bender. Some don’t. Some use very sophisticated CAD software and FMEA in the design process.
If you can, take time to visit your supplier/s in person. Tour their shops. Speak with them at length regardless of perceived quality. Talk to owners of the product you are considering. Within these walls lie many satisfied customers of multiple suppliers.
As others will tell you – DO YOUR HOMEWORK.