Mine are getting really lose as I'm pushing 120k - considering poly mounts but obviously, like EVERYTHING, can only find them for 3800. Are they interchangable with the 3400 LA1? I imagine they would be. For some reason I imagine turning my stock ones would just rip them apart...

 

They all are somewhat different.... For example:
Mines a 1999/3800, Yet my torque strap mounts are from a 2000/3800.

The 1999's were totally diffrent design...
So, id say no there not.... I had to change mine out do to extended mileage of over 160,000 miles... Definately saw better days.... I can feel the diffrence
between old amd new ones right away...

Its best to do your homework and get the correct one for your model, year, motor!

 

I've compared the 3400 and 3800 '00+ Radiator and dog bone mounts. The Radiator mount is what is different (but the bushing appears to be 100% identical). The difference is in how the radiator mount attaches to the car. Such as:
- on a 3800, the mount has 2 top bolts and two lower bolts (accessed vial holes in the upper radiator cross member).
- on the 3400, the unit has 3 bolts, 2 on the top and the 3rd is in front of the radiator mount.
Why GM bothered with 2 different designs when the same one would clearly cut it is beyond me. But the bushing should be the same. If you are nervous they aren't, go to a junk yard and pick up the 3800 mounts.

Here's a 3400 rad mount:


And the 3800 (mine to be specific):


I don't know what all engines on Pre-'00 cars GM used this type of mount on, but this was a different style used at one point. And without testing it, if you look at the radiator cross brace on a '00+ Monte, it almost looks like it still has holes to bolt this style brace up to it. I was considering trying that idea to keep rubber bushings but have SOLID rubber bushings and then shine up the aluminum dog bone (instead, I went poly from WBodyStore.com):

 

The physical shape and mounting configuration are different, but (according to Autozone & O'Reilly) the bushing itself is identical for both the 3.4 & 3.8 struts in '03.

 

Yes the bushing are the same.... But the mounts are definately different...
Mine is the 3 bolt style....2 on top and 1 in the front of the radiator core support...

Unfortunately your local auto parts has to sell you the whole mount....and dont offer the replacement bushing seperately...

 

True, so if you want to just replace the bushings you replace the mount (which in the end might be better off anyways, getting those bushings out is a pain, but getting the poly ones in is a piece of cake).

DenaliZO6 is wondering if he can swap his aged 3400 bushings with poly, looks like the answer is a confirmed "yes".

But, if he changes his mind, getting replacement mounts should not be a big deal.

 

Thanks everyone - that is what I suspected (knowing braces/mounts etc.) would be different but that the bushings seemed to be interchangable. I see some polys in the near future...I will post if they don't fit. As for getting out the old ones...I've read the horror stories, but they will come out one way or another.

 

I should have tried to WD the old ones I removed. I instead ended up cutting them out. Just a real chore.
FYI - I have the WBS poly mounts in the dog bones AND the radiator mount. It does generate some vibration feel in the cab. It's not the teeth rattling some people claim. I only feel it when I am in the car and at a stop sign or red light and holding the brake. Some days it annoys me and somedays it doesn't (if it annoys me, I pop into neutral and it's almost all gone).

Just something to keep in mind.