Hello Clayton, Your picture DSCN5502 on the old Vasa forum seems to show slots with pulleys in the cheeks which support the cross-tree of the lower main mast. Do the main yard lifts go through here? If so, what leads go through the large blocks strapped across the lower main mast cap? Would your answers be the same for the foremast?
I can answer. The foremast and mainmast both have sheaves in the hounds below the trestletrees for the halliard ties; these were bronze on the mainmast and survive, and probably wrought iron on the foremast (do not survive). The eyebolts in the underside of the cap are for the toprope (one for the dead end, one for a single block). The upper block for the lifts is a pendant block of a peculiar form, long with a hole in each end (pendant and becket), probably made fast at the underside of the top.
The halliard ties are fastened directly around the fore and main yards and as you say are for lifting the yards. One end of each of the ties goes through one of the sheaves and down to a block that has a sheave in the top of it that is perpendicular to the lower block sheaves and then back up to the other masthead sheave and is made fast to the yard again. The lower end of the block and tackle near the deck utilized sheaves in knight heads at their lower end. On my model, the main mast halliard tackle uses a knight head on the upper gundeck, and the tackle goes through a hatch in the upper deck. (If I remember right, I had to modify the deck framing a bit to get it to work) The foremast halliard tackle uses the big knight head abaft of the foremast and to the starboard side.
The topropes are for lifting or lowering the topmasts through the hole in the top that is framed by the trestletrees and crosstrees, and that is left open by the center square hole in the top. This would be done in bad weather or when rigging the ship down for winter. (Maybe there are other situations that I am unaware of that Fred can add, I think the rare occasion of rigging the topgallants might be another.).
Hope this helps, and maybe Fred can add to my answers.