looks like 65 stuff to me, the J305 would have been installed in a 66 model year car.

both of these blocks will careful installation of the cam bearing and a cam with a grooved rear journal. This is not optional no matter what some machine shop guy claims.

 

both of these blocks will careful installation of the cam bearing and a cam with a grooved rear journal. This is not optional no matter what some machine shop guy claims.

I built a 961 block, and my machinist (who had been a engine assembly/machinist for years) and I installed a non-grooved cam... He brought up the issue himself, and I questioned him on it, but he said he used a spccial bearing that have a groove to compensate (its been 20+ years, so I don't remember exactly what he said). No special machine work to cam or block...

Even with a hydraulic flat tappet cam, there were no problems, plenty of oil to the lifters and rocker arms... Ran great for 5-6 years without problems. Sold the car, and spoke to the buyer several years later, and still no problems...