Re: engine guards
The two shown in the previous posts are the only two I know of that are made "For" the VN750. Anything else has been for another motorcycle and modified to fit the VN750.
Best bet then is to find someone that has done it and find out what they used and what modifications they made.
Patriot Guard Rider
2000 VN750 Sere (Serendipity)
1990 GL1500 (Ole Blue)
1986 VN750 EVie (project bike, heavy custom)
VROC # 11628 / 25000-H
ARVROC # 12 Coordinator and Crowd Control
OKVROC # 18 (H)
TNVROC # 45 (H)