Frazz -- "Mitch, if I go with 1.12 or 1.18 will that put more stress on the K-member and frame? Would you suggest getting subframes then? Remember, my car is only street but I do want a better ride."
From my own experience, in the 1980s, I had past discussion with factory Chrysler engineers while at a trade show.. talked about adding SFC. They commented that the Chrsler unibody (referencing my E-body) was very strong to begin with, so, unless SF would be welded inplace, they would not add much rigidity, other than adding weight to the car. At that time, my SCCA Solo/autocross rules did not allow welding SFC to the cars (in category "Street Preprared"... my class E/SP). So, I've never added SFC over all these years... 20+ years of hard competition autocross. I emphasize that I've had to follow sanctioned rules for my car's purpose of use.
My car is fortunate to be 99.9% rust free and very solid. Over ll these years of ownership[ (since 1976), to datye, no stress cracks anywhere can be found. The p[rogression towards ;larger TB, and stiffer/flatter leafs, and different shocks, and large custom sway bars (1.25 f, 1.0 rear), and ultimately using very soft 40 TW tires (Hoosiers).... stil.. no cracks anywhere... K-frame is A-OK; unibody is A-OK; doors align near perfect, etc.
I'm aware that the socket in the K-frame for the TB could, if rusted, possibly tear and need welding repair... I've seen this happen ONLY on rusted cars... regardless of whatever size TB... even stock size TBs. That socket could be pre-re-inforced eventualy, just to avoid the potential tear from happening. My K-frame and overall unibody have no aftermarket mods (actually, not even allowed by the SCCA 'Street Prepared" rules)... Other club's rules may allow that... maybe someday I'll do those mods.. for additional old0age reinforcement? buy throu all these years, my car has survived A-OK without any stress cracks or welds breaking.
I do have plans to add SFC (attached only front/rear... fully contoured/floor welded are not legal in my classes/clubs, etc); the SCCA eventually allowed welded SFC... only f/r attaching points.
I know some e-body owners who've put ~1.12 TB into their cars... they love them for the street!... and have further considered stepping up to the 1.18 for the street.
I drive on the street with my 1.24 TBs with BFG 255-60-15 fronts, 275-60-15 rears (both 8" wide vintage minilite rims)... the ride is perfectly A-OK... local streets, as with any drive, have to watch for pot-holes, etc.... but on the open roads/highway its awesome... flat/stable... a pure joy in crusing!... not harsh at all. BUT.. for competition-type events (HSAX/HPDE, road course lapping sessions), I drive on BFG 255-50-16 G-force Comp-2 f/r, 8" vintage minilite rims.... the ride is still A-OK on the street/hwy, as well as increased handling on the road courses.
You won't be disappointed with ~1.0 or 1.06, but... you'll see that they don't offer much noticable improvement... and you'll wonder about the slightly larger TBs, such as 1.1, 1.12, 1.15, 1.18 that are readily available. All of these larger TBs will enhance you street/hwy driving pleasure much more than 1.0 or 1.06. The K-frame and unibody are reliably stronger than most people think... unless your car is already consumed by a lot of rust.