Alise 5-Inch Length Stainless Steel Flat Bars Straight Brace Heavy Duty 3-mm Thick Brackets Mending Plates Repair Fixing Bracket,4 Pcs Matte Black Finish

Your best bet is to put flat mending brackets between the back of the engine mount and the frame. Use the bolts on the rear of the engine mount to hold the mending bracket in place. It looks like you have plenty of threads left on the rear engine mounting bolts. Measure the distance between the holes on the back of the mounting plate, and try to match it to the hole pattern of the mending bracket. You will have to adjust the round seat tube bracket accordingly. Mending Bracket AKA: Repair Plate, Mending Plate, Straight Bracket, Joining Bracket, etc. Below is just and example. You will have to search for a matching hole pattern. https://www.amazon.com/Alise-Stainless-Straight-Brackets-J7340B-4P/dp/B08BK372JK/ref=sr_1_6_sspa