Looking to source some rockers for my 250 I am building. I have come up with Comp Cams 1629

Does anyone have experience fitting these under a stock valve cover?

I had to look those up. 1.7 ratio for 3/8 stud.
First you will have trouble getting them to fit under a stock VC. You may get it done by bulging the front and rear of the VC with a ball peen hammer and some time. The internal baffles will need to be removed.

One more thing about the 3/8 rocker studs and roller rockers. The bolt boss will likely hit the bottom of the roller rockers. It is best to pull the studs and machine the boss's down and thread for screw in studs. 7/16

Loosing lift too, going from stock 1.75:1 to 1.7:1. Assuming the factory specs are accurate, which they tend to be optimistic.

Thanks for the input. Are there any options for anything other than a stock stamped rocker that will fit under the stock cover? I'm not doing much with this engine but would like to make things better where I can.
So far I have the lumps with the larger valves and going 60 over with 307 pistons

Nice that you found the 307 pistons. Yeah, I don't know of a rocker upgrade without also sinking a good chunk of cash into a new valve cover. Would like to be able to do the same too. Keeping it low buck.

The only pistons I could find were the sealed power 295p. They have the chamfer around the edge though but it's not really that big.

There is a valve cover spacer available....

Ah, I thought you meant the stock factory 307 pistons. Then you don't have much compression other than what you could gain off decking the head.