The block casting number looks like a date code.
I can not find a record for a SBC head casting number 3905398. Were did you find this number? The only SBC head casting with a triangle on the front of the head is casting number 3947041. If it is a casting number 3947041 it will be a 64 cc 2.02"/1.60" head off of a L-48 350 made from 1968-'71.
The L-48 is the original 350 cu in (5.7 L), available only in the Camaro or Chevy II/Nova in '67 & '68. In '69 it was used in almost everything; Camaros, Corvettes, Impalas, Chevelles & Novas. In 1970-'71 it was used only in the Corvette and made 270 horsepower (base engine). It had a hydraulic cam and a Quadrajet four barrel carb, with cast pistons and two bolt mains (pink rods).
I decoded your information on the cowl tag in another post.