I think you may want to make sure you won't be burning up your rearend as well. the gearing maybe different with more power. So if your rearend is made to run from the Six, it may be over powered and burn your gears out.
99% of all gear ratios were used in all rearends in all applications across the board. im still using my factory 291 gears from the slant with the V8. the same gear ratios that were available with slants were available with V8 cars. there is no special slant six gear ratio.