Ronbo, et.al;,
The reason I specified "Flange Nuts" is that they will NOT back off. I guarantee you put one of those on hand tight you will have to use a wrench/socket to get them off! Especially since they are biting into fairly soft aluminum.
Nylocks wear out and are only verified for one use. If not serrated flange nuts, the studs have to be at least 3/4" longer. Not a big thing, but I have this thing about blocking air particularly in this instance. No an extra 3/4" stud with a bigger nut will not cut down that much velocity/volume of course, but with four in place it/they could cause a "vortex of air going into the carb" possibly creating a miss or stumble at high speed ? If it should think how long it would take someone to find it? New plugs, plug wires, rebuild the carb, check intake of fuel and passage to the carb, start with the electronics???
To answer a lot of your questions,
"these" are true lock nuts & bolt.The heads are solid as well as the flange around the nut. No lock washers are necessary and are more of a hinderence.
"Every" nut and bolt that I use in my builds are of this type hardware. Hundreds of cars and thousands of fasteners later I have never had one work loose!
Just my thoughts...
DV