[Synchro909]

Because the cooling system in these cars is not pressurised, a repair there does not have to be very strong. Let me ask this: How long has the JB repair been there? If it was done by a previous owner, how long have you had the car? Was it leaking?
While the comments about fix it right are fine and likely will give peace of mind, I'd consider another repair like the one you already have but I'd first see if there is some material available these days that might be better than what was used first time round.
If this is not an engine that means anything special (like matching numbers), I'd ditch it and for waay less than he repair with no guarantees will cost, buy another block for your rebuild.