Im replacing the heater core in my 1989 s10 blazer 4.3 with A/C. Everything seemed to be goin smoothly till it came time to install the new aluminium core and come to find out the brackets/ retainers dont fit. The core fits in the box but non of the holes line up to lock it down. Im not sure what to do. I assume i shouldnt leave it loose in the box. Anyone run into this before? I already checkes my part numbers and everything seems to match up. Any input helps. Thank you.