365 to 385 pounds all up for the 3.3 liter. It varied beftween 2.77 or 3.03 high and low mount blocks.
410 pounds for the non a/c, non power steered US 250. (45 pounds extra by my reconning)
When the 260/289/302 came out without a/c and p/s, it was 465 pounds. (100 pound extra, but they generally came with a 60 to 80 pound heavier 8 or 9" axle, and sometimes a York A/C pump and Power steering.
The addition of a York A/C pump and power steering, a Toploader gearbox and an 8 or 9" axle can then add 150 to 240 pounds to a car. So a small block 302 can end up weighing in at 340 pounds heavier than the base 'stripper" 200 cubic inch I6.
The 300 is about 470 to 490 pounds, and extra 105 to 125 pounds
The 351 W is 540 piunds, an extra 175 pounds.
The 351 C is a nominal 569 pounds as Boss 351 (204 pounds extra).
A high nickel Aussie block NASCAR 351C block with a/c, p.s. is 719 pounds all up, 354 pounds heavier than a 200 cubic inch small US I6, even before you've added the required stronger axle.
A US 351M, 400 and 429/460 is about the same as that,
Our log and cross flow 3.3 and 4.1 sixes, even with aluminum heads, were much heavier than the US I6 engines due to nickle content and lack of advanced US style egg shell bore castings