front disc brake conversion

Thanks everyone, a parts car is definitely not an option as i already have 4 cudas....me i would love to have 7, 1 for every day of the week. none of the parts cars have db setup. There is a set of kh spindles on epay right now for $75. I didnt know if it was a good deal or not. Why would I use a 73-up db as opposed to 67-69? Is that because not quite as rare?