I have a friend that has the 350 HO in his 69Z. It runs good and has great street manners. I went with the ZZ383 in my 81Z and the performance difference is big. The stroker has more torque and gives the car way more low and mid range power which is what you want for the street, and a fairly heavy car. The 383 burns more fuel though. The 350 HO has a 650 vac holley, my car has a 750 DP holley. Both need 93 octane. Seems this is where you make the jump in money and performance. 350 hp going to 400+hp. Lots of good engines out there, just my experience with these 2.