On Fri, 8 Jun 2012 12:48:28 -0700 (PDT), Evan
wrote:

On Jun 7, 4:54*pm, "Doug" wrote:
On Thu, 07 Jun 2012 12:10:42 -0500, dpb wrote:
On 6/7/2012 11:42 AM, Davej wrote:
On Jun 7, 10:23 am, Jules Richardson
*wrote:
On Thu, 07 Jun 2012 07:25:23 -0700, Davej wrote:
...
there are three 2x4 spans across the garage to form the bottom of the
"A" in addition to the tops of the two end walls -- so a span about every
five feet.

That sounds very close to my garage, both in terms of age and
construction. It's a two-vehicle garage, so the spans are quite long (I
think my spans are probably every 3 feet or so rather than 5). At some
point the side walls started bowing out, so someone punched a hole
through the top either side at the halfway point, then slung a 1/2" steel
cable across to stop it spreading any more :-)

Yes, I would trust a cable more than these 60 year old 20 foot long
2x4's.

The problem isn't the 2x4's; they've certainly got more than enough
strength in tension. *The weakest point is almost certainly the
connection not the material.

The problem is as your first posting noted the effects of a leak over
the years causing the joint to fail or perhaps the ends have also enough
damage overall besides simply at the nailed (presuming) locations.

If you pull it back in shape and gusset it up back to solid material
including a scab or two if needed to provide solid material and then fix
the roof leaks it should last indefinitely.

If you're really ambitious, add an additional one between the existing.

If I understand the OP question correctly, I think I agree with you.
Too many people worry about the material not realizing often the
connection is the problem or the weakest link.

Sounds like it is time to cut out the rotted materials
and bolt the structural pieces back together with a
proper connecting plate...

You are probably correct but I think it's safer to just start with all
new stuff. I know it adds to the cost but I'm thinking of safety and
longevity down the road. Of course that's the OP call.