A 833 Transplant: Trunnion Flange to Slip Yoke Conversion

I am looking at doing the conversion to gain the 3.09 in my 69 Dart . I want the low first to bring my rpms up into the cam while tooling around in first.
Question is will the Slipjoint conversion driveshaft be strong enought to launch a solid roller 408 at the strip from time to time ?
If it was going to be run at the strip regularly I would stick with the stock first gear and 68 trany.