I can't see how the house porch roof is supported, but that should not be attached in any way to the pole barn. They will move independently from each other and the house (not to mention that may change your tax assessment as you would have one structure, not an accessory structure).
There are a handful of ways to enclose walls. Your wood girts are fine. However, you need the gable ends to continue to the roof purlins (so extend the "cantilevered" posts). You DO NOT in any way attach to the steel trusses (at least the pic looks like angle iron truss instead of bar joists), they are not designed for that and will fold from the lateral forces on your gable ends. There will be some details to consider like soffits, headers/jambs (beyond just using the girts) for OH and man door, how the wall meets the slab/extends past the edge, etc.
Here is a photo I just pulled off the net to show an example of how they did not attach any bracing or the gable end to the trusses.
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P.S. I can't tell from the headlight shape, but that looks like some sort of IMSA buck or rolling chassis there?
There are a handful of ways to enclose walls. Your wood girts are fine. However, you need the gable ends to continue to the roof purlins (so extend the "cantilevered" posts). You DO NOT in any way attach to the steel trusses (at least the pic looks like angle iron truss instead of bar joists), they are not designed for that and will fold from the lateral forces on your gable ends. There will be some details to consider like soffits, headers/jambs (beyond just using the girts) for OH and man door, how the wall meets the slab/extends past the edge, etc.
Here is a photo I just pulled off the net to show an example of how they did not attach any bracing or the gable end to the trusses.
P.S. I can't tell from the headlight shape, but that looks like some sort of IMSA buck or rolling chassis there?
