Starter problem HELP!

[cstm68]

Replaced the starter on my 327 the other day and all it would do is grind, I pulled it out and took it back the the parts store and he told me he sold me a hi torque starer. He swapped it out for a standard one. I got that installed tonight and now it starts rite up just fine most of the time but 1 or 2 times out of every 10 starts it grinds. But the next time I turn the key it starts fine. The starter is a little louder than the old one but I'm not worried about that. I can't shim it because it is the style that only bolts the the bell housing, I'm running the bell housing from a Saginaw 3 speed what should I do? My block is drilled for a 2 bolt starter that can be shimmed, should I try that style starter?