oh, help! code has changed, crawl space won't accomodate required size h20 heater!

[Cindy Ace]

I sure somebody can help me. My property was built in 1986 on a crawlspace. It's got a 38 gal electric hot water heater (a short one, since the crawl space isn't big enough for the normal size) that just died.  I've found out that since it's a 4 bedroom, current code now requires a 40 gallon. Can't find one locally.

Can I just get a 38 gal and get somebody or their uncle Bo to install it or is that begging trouble for the future?

Thanks, dear new friends. I'm new at this whole thing...