Mike, I just went thru this with a 327 and a 430W I got with out trays, back plates and connectors.
$175 seems a little high unless it includes a connector kit. Plug, back shell, pins and hold down.
What I ran into was many on eBay do not have the connector kit at all and some even don’t have the RF adapter. But there is hope. Most All the parts for the kit can be sourced from Digikey and they are the exact same ones Garmin included originally. The hardest part to find is the hold down bar. You might have to get a 430 set on eBay.
Here is one that looks good but does needs the connector kit.
eBay [
ebay.com]
I can give you some links to the connector parts if you need it.