Need 318 Gurus

I'd use the front of the blue motor for a 75 Ramcharger. More factory correct that way. It would include pulling the oil pan and timing cover too, so, you can check bearings, install the correct oil pan and pickup, replace timing chain set if necessary, and check the valve timing.
I believe trucks and for sure, Vans, have the oil sump reverse from the cars. You will need to change that along with the pick-ups tube and strainer. Years ago I installed a 69' 340 into a 72' Van and just changed over all the external items and it fit well. Note: had to fabricate the motor mounts(340 and 318 were different). The 340 never came stock in a Van. Also the truck and vans had a one qt. larger sump.