LM7 was one of the RPO codes for one of the 350 motors in these trucks, and there were several. depending on emisions equipment and GVWR level. 6200lbs GVWR was the cutoff for emissions equipment levels(the 1970s years F44 RPO equipped and BIG10 trucks etc 'cheated' this federal requirement).
there were several 350 motors including vin digit code L and code M and so on ones... over the years. code L was light GVWR more emissions equipment, ESC/EST with the E-series carb and knock sensor timing retard funtion HEI system) and a catlytic converter and so on... code-M 350 motors usually didnt have the others and basically had EGR and relly no other emissions equipment, and had an M-series carb(non-ESC/EST).
and high zinc and phosppphorus content motor oil is what you want in all your flat tappet style camshaft motors.. luca hot rod and classic oil, or break in oi, or VR1 racing oil, etc. althoguh im not sure what the levels of the current VR1 oil are now, it may not have enough ZDDP etc in it now, so i dont use it alone, but i will use some VR1 oil just to top it off, for when it needs a little bit, from being a little low, from normal use over time. a juuug of H/R and clasic oil or break in oil is only 40 bucks on amazon. and i use what i drain out of my motors when i do an oil change for my old mowers etc. all my mower motors are 1990s or older.