SAE J442 does not limit the method of attaching test blocks. Welding is frequently used method.
J442 is the revision process now to add a statement allowing one or two extra threaded holes for mounting as long as the holes to not protrude into the strip mounting area.
Don't go crazy with the welding otherwise you may compromise the hardness of the test block. The best method would be to heat treat your entire fixture once complete.
