all '49-'58 will fit but must use end gaskets year specific to pan, typical pan gasket sets come with both styles. '59 up are a quarter inch longer and will not work.
The real J2 pan had what looked like an oil filter can welded to the side of the pan to add an extra quart of oil.
I didnt give enough information i have the oil pan with the extra quart capacity ,i was thinking about 303,324or are they different ,and if so what year ?the plan was to get a way from the quart sticking out the side.
The 303/324 pans are a bit shallower ( about 1" ) than the 371's. I found this out after spending $225.00 to have my oil pan chrome plated and the baffle in the pan ends up hitting the crank. As for the "tin can" , on one pan I cut it off and welded the hole up and on another ( the one I ended up using ) I just shortened the can enough to clear the header.