Looks like you left a letter out after the G? At any rate what you posted breaks down as a:
G-Series (1971 model year) 340 P = Premium Fuel October 24th 1970 Assembly date 547th engine assembled
Cool engine, but you better have lots of race fuel around with those pistons, that is one old school build! IMO I'd tear it down and start over with all fresh parts, pistons, rockers, etc. Maybe even the heads if those have been overly ported.
