I think you have a pretty fair chance of making that fix work. It is not "by the book", but a lot better than most Bubba fixes. The crack is on the exterior of the block and it is not somewhere that is going to get really hot (like around a valve seat).
The machine shops on the destroyer tenders use Belzona to rebuild the blades on centrifugal pumps that had eroded away from cavitation.
First pic is after I applied the patch . I taped off the area to apply patch, then few minutes after removed tape. Second pic is after 3or 4 hours put it under heat lamp of heat gun for several hours to increase strength. I put it in the sun . After it cured a while, it looked like brand new steel.
Got a lil more done today . Didnt have rear cross member so got one from Walck . Finally got around and got the rear cross member installed or fitted up , not installed .Also removed the v shape rear cross member support and working to get it fitted up. Why was the v support not right ? The new one. Way to long.
Bmorgil is correct. The majority of the reproduction parts are designed to fit several different models, so some trimming is required to fit the early, shorter frames. Your rear crossmember looks great.
Got the v brace fitted up. And tried to do some sand blasting on frame but it was a pity, not enough air to run properly, got some done but really a Bubba job, so did the hardest parts to get too , going to plan B, OSHPO ,for the finish. Question does any body make a copy of this battery tray or just use the generic one ? Most replacement trays Ive seen do not have the groove in front of tray .
Got a few more things done. Repaired the grill mounts on the frame . And cut off center grill mount from the cj2a frame and gonna mount it on the cj3b frame . But running into front fender mounting issues , some of the holes to mount fender from cj2a frame do not jibe with the cj3a frame. Front shock mount on cj3b frame is different than the front shock mount on cj2a frame and causing fitment issues with fenders. Only have pics of the outer grill mounts and the center bracket to be welded on. I want the grill and fenders to bolt up for proper center grill placement of the center bracket. The first pic shows no center grill bracket second pic shows bracket that I removed from cj2a frame and gonna weld it approximately where it shows in pic 2.
In my opinion, I would fix the fenders to where they fit the 3B frame to clear the shock mounts. Mark the spot that the shock mount is on the 3B frame, then cut it out. Take the metal removed to fill in the 2A shock mount hole.