Well Stoker man The AP- 520-1 boiler weighs 750 lbs and the Sq top AP- 350 boiler weigh 575 lbs Now maybe the new DF 520 boiler weigh 800 but not the older AP-1 520 and being the AP-350 where made around the same time the weight
on them are right out of the EFM forum AP-245R - 67 and also being I moved or Pick up 1 2 or 3 on any given weekend
I know how to get them out of basements and what they weigh and 95 % of them where made in the 50's and 60 s
and last month I help get 4 Sq top 350 and 1 round top boiler and will be picking up another round top 350 next week
I know how much they weigh as well And On Saturday if I did not do the Tour I would of been helping picking up a 700 which weighs a total of 1833 lbs would you like me to break the weight down for you and size Jusk for kicks

Ps did you see this thread on moving a boiler ot of a basement
http://nepacrossroads.com/post71026.html I used the the floor joist trick
when i did mine Plus alot of the older house in my area had bars already in the Joists Mine did the old timer used that meathod alot when they put them in or out and I will be using it next week when We go get the other Round top boiler 350
AP-700
Boiler 1100 lbs
Base 226 lbs
stoker 375 lbs
Jackets 132 lbs
Total Weight 1833 lbs
Base size without Jackets
42 3/4 " long 29 2/4" wide 23 1/2 " high
Boiler with out Jackets
42" long 29 1/2 wide 33" tall