3.09 4 Speed Gear Set Strength

Can I use the slant 6 / 318 gear set with the 3.09 1st gear behind my built 340 stroker motor?
I want the low 1st gear to offset a 3.23 rear axle ratio. Tranny guy was questioning if the gears were as strong as the 2.66 or 2.47 gear sets. Will they hold up?