Hoss, has the heifer been tested for Chondrodysplasia (I'd guess non-carrier) and PHA? It's good to know her status even if she is AI'd to a non-carrier of either. Who's her sire?
I'm sure you realize there are no EPDs for Dexters. I believe all the AI bulls listed here are negative for Chondro and PHA. Here's the ADCA list of AI bulls:
http://www.dextercattle.org/AI%20Bulls.htm
Personally, I like Cache Mudflipper except he has horns. Semen is reasonable at $25/straw.
If you absolutely positively cannot have horns, I also like Hillview Red Wing, but semen is $65/straw.
If you find what you like, the owners can probably give you an idea of calf birth weights if you ask them.
Does this help?