I have a 1977 ford 351 V8 auto transmission...It goes into reverse great but not D ,2 or 1 until after several several times
These rig were subject to the shift tube's alignment pawl shearing off, the shift collar breaking on the inside collar ring,shiftier bushings wearing out unusually fast, and if someone got rough with it the linkage rods themselves bending, so if everything I have mentioned has been checked and is in proper working order then I would recommend that you take it to a tranny shop so they can check the pressures and check the valve body for proper valve operation, as you mentioned it works after several tries, the valve body may need overhauled or replaced due to varnish.
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