Flex plate, 168 0r 153

[slam33]

I'm finishing up the rest of the parts for my conversion to auto. I got a test bed tranny that I will slap in first before the hi/po 350/Gear Vendor unit goes in. The tranny came out of a Chevelle 350/350 with a 153 ring gear. I have a 168 but I think it's for a 400 exernal balance ( it has two sets of what look like balancing holes around mid diameter ). I have to buy a starter for the conversion from stick to auto, I only want to buy 1 starter. Anyone find any problems with the 153 gear or is the 168 worth the money.