Removing the underslung saddle block won't cause issues with the leaf spring but the chassis will have to be supported before you loosen the axle U bolts which hold it captive. It does appear it has a tapped hole within presently accommodating the sheared anti tramp bolt fixing. The tapped hole may have been the only solution if clearance wasn't available to accept a nut the other side of block. Its possible you can use an "easy out" to remove the sheared remaining part of the bolt, having drilled a liitle way down its centre. A matching bolt with the highest shear resistance could then replace it. Failing that a new sadldle block may be attainable.
As suggested in the GoMog article the use of only one anti-tramp bar is cutting things fine engineering wise but guess the arrangement has survived a number of years. A second anti-tramp bar and matching saddle block on the other side would be far better of course..
