I am wondering if it is OK to use the stock style lifters in a gen vi 502. The cam installed is crane 168741. .610/.632 lift. Crane says to use crane lifters with lift over .570.

Are they just trying to make money or are different lifters required?

Do what Crane says.
MY 2¢

With my 741 I used Crane lifters, springs, rockers they recommend.

Baja,

The GM OEM roller lifter will accept a range value of 0.326” lobe lift (0.555” valve lift) to .335” lobe (.6035” valve) to insure the lifter body will not drop below the base of the retainer plate when the lifter is on the base circle. If you attempt to utilize an OEM lifter to a .372” lobe cam you will need to mock up the engine to finished spec and validate that dimension.

Bob

I used a set of stock lifters on a .625 lift cam and they worked fine. Just make sure that they do not hit the retainer plate at the top of the lift and make sure they don't go below the plate when on the base circle.

It’s important to differentiate between stock style lifters.
The GM OEM stock lifter is problematic due to the shorter body and likely will not have the dimensional length to accommodate the specified cam. Many of the Mercury Marine stock lifters are actually the Crane/Morel .300” long body lifter which is compatible with a .372” lobe lift on the Crane Cam.

The other thing to keep in mind is that the stock hyd lifters may not be able to handle the increased spring pressure required for proper valvetrain stability with a cam that has that kind of lift. The stock lifter also has a relatively small wheel on it. My advice is to spend the money now and get your valvetrain set up properly. You will regret it if you "cheap out" in this area. Ask me how I know.

I am asking as this is the set up in a 502 I bought here a while back. The engine was professionally assembled from what I was told but before putting this one into service I wanted to get this figured out.

Baja,

Email me a photo and I will let you know what you have.

Bob