After recently removing the front prop shaft on my DII, I was forced to replace the four bolts with grade 8 bolts (same size) due to lack of local availability of the stock bolts. Does anyone know if this is a major issue and whether these need to be changed ASAP?

 

Shouldn't be a problem as long as you used lock-tite.

 

No lock-tite, but I did use lock nuts.