well I am sure it has been well covered but I'm too lazy to search. I have been driving my old 61 half ton GMC a fair amount though not daily. and it is a fairly worn 305 V-6 4 speed. a friend has a cousin with a rebuilt straight 6 out of about a 61 or 62 2 ton grain truck. seems like he said around 265 cu. inch. anyway if at some point I can get it without too much cash flow- I'm wondering if there is anything major I should look for in swapping. I assume the old 4 speed will be fine but probably bell housing and clutch will be different? likely have to change driveshaft length as well.I don't even know if it includes manifolds and carb or not but just wondering about what major things to check for. I currently have my radiator in the shop and they tell me it is beyond repair. they offered to put in a new 2 row core for cheap. I expect since I'm not pulling it hard it likely will keep the old engine cool enough but I may need to find a fan shroud to pull more air through it.