I used one from American Powertrain in my big block Coronet. The installation took some time, but nothing I would call crazy. You give up a little firewall space for the master cylinder and pushrod. You also have to carefully measure clearances to select spacers for proper throwout bearing...
Get the kit from 440 Source. I put one together and have no regrets. My machinist wasn't happy with their balance job, but that was the only negative I can speak to. Makes ridiculous power with Indy EZ heads.
Brand new .030 over IC745-030 ICON forged pistons w/+20.5cc dish and CR3690 030 Total Seal rings for 408 stroker. After I bought my Scat stroker kit, the block I planned on using didn't clean up at .030, had to go .040. My loss is your gain. Summit gets $775, I'll take $650 shipped to the lower 48.