Just wondering;
Would it not have been better to maintain the Glencoe attachment method, or are you intending to upgrade the drive-train to match the Stryker attachment method?
Back to your question with an answer.
The Glencoe Mule wheel hub has a spindle that is supposed to attach to a small disk that is placed inside the wheel. The wheel is then attached to the spindle so that it is free to rotate if attached and glued properly. It all looks easy on the instructions but it is a bit janky when you have to find a way to glue the wheel to the spindle without gluing it all together and losing the wheel rotation. Not that I intend to roll the damned thing around on the floor but it does create some fit issues.
The replacement Stryker wheels have a spindle moulded on to the back and this feature is mated to the brake drum and the suspension arms via another circular part.
Dry fitting these parts to check how this can be modified suggests to me that the best approach to making this work will be to remove the spindle from the original Glencoe part so it becomes a flat surface and then attach the Stryker parts to it. An easy modification to allow the Stryker part to be secured to the Glencoe part.
Attached images showing the Glencoe spindle (unmodified) and the Stryker parts in and out of the modified Glencoe Mule wheel.