In 1964 there where 6 engine choices available . There where no big blocks for this year.
All engines are stamped with an engine ID code, consisting of assembly plant code, production date and suffix code. V8 codes are stamped on a pad just forward of the right side (passenger) cylinder head. 6 cylinder engines are stamped on the passenger side of the block behind the distributor. The block casting number on small block and big block Chevy V-8 engine's are located on the ledge found at the rear of the block, most often on the driver's side. This ledge forms the mating surface between the block and the transmission bell housing. These particular codes designate the specific powerplant that was installed in the vehicle at the factory. Note, this is a general reference.

Code	Power plant	Equipment
G or GB	194-120 HP	3-Speed Manual Transmission
GF or GG	194-120 HP	3-Speed Manual Transmission, PCV
GK, GL or GN	194-120 HP	3-Speed Manual Transmission & A/C
GM	194-120 HP	3-Speed Manual Transmission, A/C & PCV
GH, CJ, KC or KD	194-120 HP	Taxi Equipment
K	194-120 HP	Powerglide
KB	194-120 HP	Powerglide & PCV
KH	194-120 HP	Powerglide & A/C
KJ	194-120 HP	Powerglide, PCV & A/C
LM	230-140 HP	3-Speed Manual Transmission
LL	230-140 HP	3-Speed Manual Transmission & A/C
LN	230-140 HP	3-Speed Manual Transmission, A/C &PCV
BL	230-140 HP	Powerglide
BN	230-140 HP	Powerglide & PCV
BM	230-140 HP	Powerglide & A/C
BP	230-140 HP	Powerglide, A/C & PCV
J	283-195 HP	3-Speed Manual Transmission
JA	283-195 HP	4-Speed Manual Transmission
JD	283-195 HP	Powerglide
JH	283-220 HP	3-Speed or 4-Speed Manual Transmission
JG	283-220 HP	Powerglide
JQ	327-250 HP	3-Speed or 4-Speed Manual Transmission
JT	327-250 HP	3- or 4-Speed Manual Transmission & Transistor Ignition
SR	327-250 HP	Powerglide
JR	327-300 HP	3-Speed or 4-Speed Manual Transmission
SS	327-300 HP	Powerglide