Mike,
I replaces the plastic fuses with aluminum tubing. It is straight and smooth and a lot less work than doing all the sanding. I replaced the cannon barrels with tubing also. You are right the flared barrel ends are not correct. I have never found any photos of an A-i with flared cannon barrel ends, including Korean War early ADs. Monogram does give you a nice mixed load of odinance, especially for Viet Nam era A-1s.
Note that the ribs provided for a folded wing are not used if you do not cut and fold the wing(s). I did a folded wing version of a Marine aircraft with the cowl opened up. I used the P-61 Black Widow engine for a base and modified it to resemble the A-1 engine.
It is white with day-glow orange panels. It is in a box somewhere. I'll see if I can find it , take some digital pics, and post them.
My next A-1 will be the Tamiya kit with an Aries cockpit kit, wheel well kit, and some other detail items. The Korean War Non-Specular Sea Blue paint scheme keeps calling me! Then maybe a Matchbox A5 with Tamiya wings modified, etc. The SPAD is just a great old bird.