What direction do you want to go, that might help narrowing it down. Personally all my hiefers get bred to my simm or angus low bw herd bulls with proven EPDs. Or if I AI I have used Hooks Shear force 38K with none pulled and good calves, Also used lucky break with good results and cows make great mothers to keep. Their heads and front ends are kind of usgly but they have not passed that along to any calves I have had out of them and raise some of my best calves every year. I have used BC lookout with good results calving but have never had any calves impress enough to keep any back they also did not have much frame or growth to them in the feedlot. As for clubby bulls I personally wont recommend one of them because the only one I used was ALI and had nothing but problems. Bred 5 heifers to him and only 1 calved unassisted and never really liked any of the calves either. I have herd Smokin Joe (Ali son) calves easy and he has proven EPDs and good accuracy, so he is prob the only one I would ever try myself. That is the thing to watch is the accuracy. Ali never had good acuracy and he throws some small but throws some huge ones as well. What I have found is even if you get lucky enough to get a live high powered clubby calf out of a heifer with the calf and heifer still alive I would say prob only 10% of heifers out there can really raise that calf to full potential. I wait until they have 2 calves before going high powered with any of my hiefers/2nd calvers. I just don't have hardly any trouble and the calves grow to their full potential on most all 3 year old cows and older. And that one year I had everything from C section to another heifer that went down and never recovered. I had 95% troubles and 5% success just one year and that is not worth it to me.