Without major mods (moving engine plate or shortening axle), that's probably your best option & there's a number of ways to achieve it; IMO, the best way is to use full thread bolts with nuts as spacers, keep adding nuts until you reach the desired distance... but, don't go nuts (sorry, bad pun...)
Just remember, I may be good but, I'm not perfect & I'm no engineer (although my buddy says I am 'coz I have an engine 'ere & an engine 'ere & another engine 'ere ), my solutions are based on experience & basic engineering principles...