I consider a small flexible roof mounted solar panel worthwhile. Something 80+ depending on budget. It is nearly always giving something. Even 15W under marginal conditions is probably offsetting hourly consumption of the average Waeco. Extends battery life and less times the folding ones need to come out. Only big ticket spare I would consider advantageous would be a spare generator due to the need to run engine fan. Even a non functioning one to act as a shaft . Other than that the usual cables and fluids. Electrical hot wiring bits. Most switches can be bypassed to get you to civilisation. CVs normally give a fair warning. Carry a spare and a few bolts if you wish. Definately check that ALL existing bolts on CVs are not damages and are torqued to 25ftlb. Carry a 1/2" drive quality drive bit to suit the bolt heads. I get theimpact ones from trade tools. A out $9 EA. Plus use quality socket and 18"+ breaker bar for wheel nuts. Also torque wrench for same. 95ftlb. One front bearing kit in case one stuffs up in a water crossing? Spare upper bolt for rear shocks. Not a common thread and can suddenly get lost Maybe X2. 1 to recut a stuffed thread and one for repair. I carry a number of common parts taps. Spare checked/ timed dissy, coil, leads, points, condenser. Spare oil n filter in case you get a sump full of fuel. Basic recovery gear for stuck off track. Snatch, tow, cheap hand winch and a few D shackles. Suitable road tyres get you a lot of places. I often carry snow chains for off road use. Easier than multiple spares or mud tyres when only occasionally needed. Slightly bigger tyres are good. Your motor if pushing stock 1600 gearing should handle common upgrade of 668mm (vs 650 stock) This gives 195 R 14, 205.75.14. for starters on 14"X 5.5" rims. Mainly made roads you will be fine. Corrugated can play havoc with carbs so if an issue check these. Nearly forgot.. Only reason for unreliability is years of neglect or crap mechanic. Once brought back to well maintained condition it's only scheduled maintainence pretty much. Plus rustproof with lanolin or similar everywhere possible. 3000w inverter seems big? Is it for any particular reason? Is it only " on" for a particular use or low standby load?