I think he should do a smoke test. Double check the spark plug wiring is correct order too as well as a visual inspection check for cracks, I’m not a fan of that braided sheathing, also check condition of the spark plugs.
On the oil temp gauge accuracy - maybe disconnect wire and see if dash gauge pegs up or down (no power) and if it has full range.
The other method is where to get an accurate reading with a IR handheld thermometer at the sender or oil return tubes….there were a few pelicans that tried verifying oil temps with a long probe-style thermometer down the oil dipstick to the oil tank. Not sure if this is with engine running or immediately off, but maybe expect a few degrees off and if anyone ever had a respectable reading if it’s possibility to check temp. inside tank.
Regardless, who knows what hidden damage can still exist with an engine fire. Any extreme heat could have warped the diaphragms within several components and that may been overlooked when replacing just charred vac hoses.
Seems to me like the fault was probably in the rebuilding. Finding and trying to “un-do” several mechanics work (too many cooks theory) is a headache especially when it wasn’t just right from the get-go.
If he sorts and eliminates the simple stuff, he can proceed to test the CIS.
Local chapter of PCA membership is a good source if find a qualified tech (or use this reference….
https://cis911primer.com/pages/test_pressures.html
The sputtering performance on the low end is being overcome by higher rpm sounds simple enough. Fuel and delivery issue relayed to extended no-run storage may still exist. Once he finds a timing light he can eliminate at least one pressing issue.
