Do any of you guys know the history about Dick
Landy Industries? I have recently seen decals
with insigna two circles DLI on valve covers and
similar stamp on front of "engine block" below cyclinder head. Was this a common practice for
DLI?

They are no longer in business, after Dick Landy's death his brother Mike and son Robert closed the shop. There were several styles of decals made, some were refelective foil like yours appears to be? Some had white backgrounds, there were also early and later versions (yours is the later version) many were put on engines they worked on after completion and some are still around unused as they often handed them out to customers (I got some from them back when they built my Hemi's) some were also sold after they closed the doors. If the "engine block" you are describing is a similar looking circle shaped insignia it is more than likely authentic, they stamped allot of thier work with that. Post a picture of that if you can.