#340690 4 5/8" O.L., 3/8"-16 thread

GM Part # 3406090 Lower Push Rod

GM's "690" lower push rod (z-bar to fork) is
approximately 4 5/8" long rod, and is threaded
3/8"-16. It is used in conjunction with a jamb
nut and a inside threaded rod or swivel, such as
the 3973076, to make proper clutch pedal free play.

N.O.S. 340690 Clutch adjusting rod
Pictures and description is from a new GM part.

Thread
3/8"-16 Thread

Length
Overall Length: 4 5/8"

Fork End

Applications per the thru 1975 Chevrolet Parts Catalog.
0.787 ROD,fork push adjusting
72        Camaro (402)
71 Camaro (400)
66-67 Chevelle (396)
70 Camaro(396)
67-75 Camaro(350)
69-75 Nova(350)
64-67 Chevelle(327)
67 Camaro(327)
68-69 Chevy,Camaro(327)
68-72 Camaro(307)
67-69 All(302)
64-67 Chevelle(283)
67       Camaro(283)
75       Nova(262)
64-70 Chevelle,Pass.,Camaro(6 cyl.)

Applications per the 1976-81 Chevrolet Parts Catalog
0.787 ROD,CLU FORK ADJ. PUSH (LENGTH 4.70)
76-79 F (V8)
77-79 X (V8)
80-81 F W/M.T.(V8)(6 CYL.)

Applications Per thru 1975 Pontiac Parts Catalog. Dated November 1,1974
0.787 ROD,fork adj. push --- (4 3/16" long)
64-65 T/6 M.T.
67-69 F/6 M.T.
67-69 F/8 M.T.
70-75 F/8 M.T.
71-72 X/307 M.T.
73-74 ALL X/350 M.T.
75      ALL F,X M.T. exc. 260

Applications per the1976-81 Oldsmobile Parts Catalog Effective July,1987
0.787 ROD,CLU. FORK ADJ.PUSH (LG 4.70")
77-79 X(V8)

Applications per the1973-78 Truck Parts Catalog
0.787 ROD,fork push
73-78 ALL

Disclaimer:

Factory correct applications are your responsibility. GM made part and part # changes with no rhyme but a reason (no production interruptions at any cost).
Application charts are for replacement parts that were available at the time of parts book printing.
My observations come from the parts I have in my collection or other reliable sources your parts may differ.
If Factory correctness is your goal, do more research, join car clubs,
forums and buy an assembly manual if one is available for your Project Car (you won’t be sorry).
This is a fun and interesting part of the hobby!