G'day Norm,
For sure. Irving does point out that the 'plane' in which the vibration occurs is important.
And compare these to the 'Victa 500 Twin', which had by far the best inherent balance of any engine Victa used.
Especially since it was a 'boxer twingle', with both barrels firing at the same time.
Edit: Anyway
Misstonz, apologies for our meanderings down a technical sidetrack here.
The upshot is, that a modern 'sloper Briggs' will be much kinder to your SB45 chassis than an older 'vertical cylinder' model.