I think you're on the right track. But yes as was said, use the 850. A kit is cheap if it's a leaker and while yes, it a little too much, it's better than not enough.

Also, PLEASE reconsider the main studs. You will need an align hone and the bolts holes on #3 enlarged. I PROMISE you, it's not worth the expense. The motor will be fine on main bolts!

Keep us posted!