The first-generation Econoline body shell did not change over the 7-year production run (1961-67), except for adding the Supervan option--an 18" extension to the back of the truck (available mid-1965 through 1967). Dating of Econolines by exterior cues is thus a question of recognizing details, supposing you're looking at an all-original vehicle, which is a rare beast.
Front turn-signal lenses were clear in 1961-1962, amber from 1963-1967.
Roof ribs were added in mid-1962 to the formerly smooth sheet metal in order to reduce road noise; this feature was kept through 1967.
Outside rearview mirrors changed from round (1961-1964) to rectangular (1965-1967).
Side trim on deluxe models consisted of bright-metal strips with anodized inserts in the years 1962-1965. Single-piece bright "narrow" strips were used in 1966-1967. The poppy-red, so-called "Deluxe Pickup" (on the invoice Ford named it simply "Special Promotion Package") was a 1965-only promotion and so wore the wide side trim with inserts.
Car-style hubcaps became available in 1965. The bottle-cap-style hubcaps are sometimes seen in later promotional materials, however.
Bumpers from 1961-1964 used a rear bumper with a recess for the license plate. This changed in 1965: Heavier units that could switch front to back were used on vans, and the license plate moved to the left rear door; pickups retained the older rear bumper with the license-plate recess.
Backup lights were available in 1967 only. On regular trucks these were round units below the round tail lights. On extended vans they were incorporated into the lower portion of the rectangular tail lights, which had always been a feature of the extended vans from their introduction in 1965.
"Heavy Duty" emblems on the front doors appeared with the same-name option in mid 1963 and stayed through 1967. "Supervan" script appeared on extended models, unless they were also heavy duty, in which case that emblem was used.