537251302 is the correct kit, partition and clamp.
Onan, the 346xp i'm working on now has a ripped boot, right at the impulse nipple. whoever installed the metal clamp, wasn't careful with the impulse nipple, and ripped it. so this IS possible.
the intake clamp in the correct kit is a bit tricky to get right. when I use them, and i've used quite a few, I grind on the tab on the clamp to make it easier to slip...and then grip. you'll see what I'm talking about. the gripper tab on the clamp is too square/sharp on one side, and it needs to be rounded. "grip" side of the tab needs to stay square and sharp.
linemans pliers work best for the clamp