I have a fingers width clearance at the firewall. Never an issue. Looks like you have plenty. But I’d go ahead and cut the shaft on the pump.
I love the HDS7 for it’s ruggedness, accuracy, and screen clarity. I also have several areas - like Moab - for which I have purchased satellite imagery. I have built my own maps for many offroad parks, and also purchased gpx files for others. I use a few mapping software packages, including Garmin Basecamp and ExpertGPS. I’ve taken Google Satellite imagery and turned that into pretty good maps for several parks in my part of the country.
That said - the Lowrance platform is a pain in the ass. It uses a propriety map data format, instead of using standard gpx files like just about every other platform. I use a conversion program called GPSBabel to do my conversions. But if you don’t get the conversion and versioning just right, it fails - and gives no indication as to why. I curse the thing every time I load maps to it.
Also, it used to be that you could build your own sattellite imagery for the Lowrance. Again, a proprietary format which requires a conversion program - built by Lowrance. That’s how places like Rugged Routes does it - that is where I have gotten my sat maps in the past. But Lowrance has now stopped providing that software, so I can’t create my own imagery.
For a dedicated GPS setup, I’ve looked closely at the Garmin Tread platform, and like it a lot. I’d consider it if I were swapping. I run the Garmin Zumo - which is very similar to the Tread - on the bikes, and I love it. No data conversions needed, and you can easily get their Birdseye sat imagery.
But if I were swapping, I’d also look closely at a platform which would run someting like OnX. There are many options these days. But I still lean toward something more rugged than a tablet.