I have 1.03 bars in my 69 Swinger, combined with Hellwig front sway bar and Billstein shocks on all corners. Rear springs are reproduction 383 GTS spring that have a slightly higher rate than factory 340 springs. In my opinion it handles great, it is not harsh at all but is firm. The car now corners very flat with little body roll. The tires are definitely the weak link in the corners. My steering box is a fast ratio Flaming River manual box. Overall I am very pleased with the results. I still have the Hellwig rear sway bar in the box I have yet to install.
Not sure I answered your question exactly, also I'm not sure of the weight difference of a small block vs slant 6.