Comp Cam 7821-16 pushrods (340 w/ 273 rockers)

Since I plan to install a hydrolic cam/lifters in my 273 that is otherwise stock I expect the " off the shelf " pushrods to work. I sure hope so since I've already bought them.
As others have said, the farther you move from stock with the cam and heads the more things change.
I think custom length pushrods would be better than shims under the rcokers shafts.