Hey now!!! I've had this EXACT problem, not 6 months ago on my 230!!! 250 and 292's are direct bolt-ins... I used one that has 2 threaded ports on the right side (looking at the engine from the front) I used one to mount the sensor for the cooling fan and the other to mount the sensor for the temperature guage... I also found a couple that have 3 ports. The salvage yards are chock full of older inline 6 GM motors so I scavanged a few... you know, to keep as spares... so go get a couple... get the water necks while you're there... always good to have... GOOD LUCK!!!
P.s. JB WELD "WILL" hold to get you out of a pinch, until you procure a replacement. Super clean and lightly sand the area where the crack is and apply JB liberally and let set for a day... It held for 3 days before it started to leak... by then I found a replacement!
