Will be trying to start a '70 914-4 (Webers) that hasn't run in 7 years. Plan to do the following:

New battery
Check the oil level
Want to avoid pulling the plugs so I'll shift the carbs off the manifolds and pour a quarter cup of Marvel Mystery Oil into each intake, put the carbs back on.
Crank it over with the coil wire off until I get oil pressure
Put a little gas in each carb throat and see it it fires
If it fires I'll put some fresh gas in the newly sealed tank and see if it will run...

What am I missing?

Thanks for your advice in advance.

Why avoid pulling the plugs? I'd def put fresh ones in. With a restart after long storage it's best to replace parts that either wear or deteriorate and reduce variables so you have less to hunt down if the engine doesn't fire. I'd include a new rotor and cap, points or pertronix, probably new plug wires, maybe a new coil. Before starting I'd also hit the carb jet stacks with compressed air and check the float bowls to make sure the floats are free and there's no varnish in them. Also double check the cast plugs on the carbs to make sure gas doesn't spill all over the engine. You mention a newly sealed gas tank. I assume that also means a new filter and replaced fuel lines?

When I started my '75 that had been sitting for 7 years, I changed the battery, checked the oil and turned the key. It fired right up and idled perfectly. L-Jet.

I bought a 914 that had been setting for 14 years. Bought a battery, put in fresh gas, checked oil, fired it up and drove it home, then to San Diego and back a week later.