742 vs 489 Case

I have a 742 case surgrip with 4.10 gears but was told it would not hold up to my expected HP levels and that I would need a 489 case....

I'd much rather use the 742 casing and jut put 4.30 gears in it and be done and maybe back brace the 8.75 too..... But I dont want to brake it only to find out it took my sprag with it...lol...

Have you guys ever witnessed a 742 failure? looking at the pictures the 742 pinion looks hulkier then the 489. I know I could go Dana but I'd like to save a few gand if I can get this 8.75 to hold up.