You'll probably do best by using an adjustable push rod to determine the proper length.  I have two that I'll be happy to loan you for the cost of shipping.  A 12" digital caliper from HF will easily give you the length you need to order.  Summit will likely have something in stock that will will be close enough to your measurement.
Let me know.
 

Last edited by Bullet Bob (4/02/2024 6:38 PM)

1.6 is the stock rocker ratio.  They used 1.72s on the Cobras with the same pushrods as the GTs.  The cam would probably have to be huge to make a real difference.  If this is a new engine build then its probably worth checking, but IME pushrod length is affected most by decking the block and/or heads.  Aftermarket heads, different thickness HG, etc. can all make a difference.  If none of that's been done/changed I doubt you need different length pushrods.

Also, you'll need a solid lifter to check length.  A hydraulic will just collapse as you try to pattern the valve stem tip. 
 

If you have a tap and die set you can make one out of an old pushrod, but the size you would need is like 11 bucks on Amazon.    The easiest ones to use are basically a rod cut with a threaded rod inside.  Thread lock on one side, and a jamb nut on the other side.   Get your length, then measure with the 12" caliper  BB mentioned . 

I had to order custom pushrods for the reduced base circle cam I used.   

If I remember correctly, 5.0 pushrods were 6.200 stock?  Anyways, just Google it.   If you have already ran the engine, it's another can of worms, because you will need those lifters to bleed down to do it correctly.   (Preload).    Your best bet if you think there is a problem is finding a mech that REALLY knows what they are doing.

MS wrote:

My suggestion in Billy’s case…
Remove valve cover.
Put #1 at TDC.
Back off the rocker bolt until loose.
Adjust to zero lash using fingers to feel the pushrod’s resistance to spinning.
Tighten one-half turn.

Did the bolt torque down properly? If so, you are done. If not, try tightening 3/4 turn. Did it torque down? If so, also done

If still loose, then you need to mark the valve tops and see the pattern. Determine if too short or too long by pattern on valve tip

I would add when at 'zero lash' to verify the rocker arm tip is close to being centered on the valve stem. 
 

Not knocking the guy, but typically guys that “were Ford mechanics for 30 years” are really good at bolting factory stuff back together but are not necessarily adept at modifying anything.

TKOPerformance wrote:

MS wrote:

Not knocking the guy, but typically guys that “were Ford mechanics for 30 years” are really good at bolting factory stuff back together but are not necessarily adept at modifying anything.

Completely agree.
 

Yep!