Morel makes them for people "hyd/solid"...like Hughes, maybe even exclusively now since I bought mine through Doug Herbert for less money "$280.00" ..that was 2011.
On the Callies/Morel website (www.johncalliesinc.com) they list two different part numbers for small-block mopar hydraulic roller lifters. The street version (PN 5321) doesn't show any oil limitation, but the race version (PN 6072) specifically states "Do not use oil heavier than 5W/40".
Here's a link to the dealer list from their website: John Callies, Inc. - Dealers
