I have run a 10 bolt in my 66 Nova for 10+ years behind a 406 small block and a powerglide with a 5000 stall converter and trashed many posi units. The only thing to help any of the 10 bolts is to put a mini spool and aftermarket axels. The aftermarket axels are heavier and thicker but the spline area of the axel is still the same size the factory axel which is the location that the axel will fail.

My recomendation is that you put a 12 bolt chevy rearend in or a 9 Ford like HWORREL suggested because a 10 bolt will not survive the weekend warrior abuse with a manual tranny. Big block or small block doesn't matter since the manual tranny is actually the one abusing the rearend and naturally the more power you have the more parts you will break.

12 bolt or 9 inch will save you many headaches down the road.