[AZKen]

The "Sticky" is this whole website. The 16 forums, Jolly's info, the search functions, VIN decoder, archives, links, members.

Jolly's Legacy pages pretty much tell a lot that you want to know. All the 305's are the same stroke and bore, same compression as you said. Most, if not all parts are interchangeable even though the design for performance or strength may change. Here is a direct quote from the day (from Jolly's page) "Many major parts are interchangeable within all GMC V-6 engines to provide greater parts availability and standardization." When someone needs a specific part, they search the archives here or ask a specific question. Jolly does have a
"Known parts" list also. There are Guru's here to tell you what part to buy and where to get them. That's what the site is for. In printed form: That's what old parts books are for. That's how you get the "overall info." But most just want to know about a part for the truck they are working on.

I agree how curious the weight difference is..102 lbs from high to low.
Reason as follows:

1. Literature mistake
2. Casting/strength changes (wall thickness, passages, etc.)
3. Some weighed motors had/included accessories mounted, some didn't. (as in: short block/long block replacement motors)
4. Material changes. (pretty cool they have aluminum pistons)
5. Some may have been weighed with bell housing and clutch or automatic trans housing
6. Weighed in different years with different scales
7. I don't know, that has never kept me awake at night.

I guarantee that at least one of those answers is correct.