Flip the chassis (get a couple of mates to help) so that it is upside down to fit the drawbar.
Cut the main drawbar sections and roughly align the back ends with the 1675 mark on the chassis.
Pull the front ends of the drawbar sections towards the centre until they are touching.
Adjust the back end of the drawbar section so the outside edge of the drawbar section is flush with the outside edge of the side chassis rail and tack weld securely.
Find the centre of the tongue brace and tack weld it securely to the centre of the drawbar tongue flush with the top (when the trailer is right side up) of the drawbar.
Clamp a couple of pieces of steel under the front end of the drawbar sections so that it can support the weight of the drawbar tongue while getting it in position.
Run a string line from the rear of the chassis down the centre. Adjust the drawbar sections out to fit the tongue and adjust the tongue until the correct position is found with the string line.
Tack weld into position.
Double check that the tongue is straight and aligned to centre by measuring diagonally from identical points on the end of the tongue back to identical points on the chassis.
Once sure of the alignment, tack weld the drawbar securely into position.
Align and fit the pulley beam to the drawbar. Tack weld only at this stage. Fully weld only once the pivot arm has been fitted to the chassis.
Before fully welding the drawbar, fit the drawbar gussets as shown below. They can be fitted with the chassis still upside down and note where welding is NOT permitted. See here for more details - Drawbar welding
Fit the drawbar top and bottom plate to the front end of the main drawbar sections to tie them securely to the drawbar tongue. Check the drawing above to ensure that no welds are made transversely across either the top and bottom of the tongue and drawbar sections.
Australian Trailer Builders -
Now is a good time to fit the safety chain to the trailer - the safety chain must be permanently attached to the trailer (welded) and the weld must extend around 50% of the circumference of the welded link and the adjoining link must have free movement.
Weld the safety chain as near as practicable to the coupling. If fitting 2 chains, they must be mounted on either side of the centreline of the drawbar.
Before you flip the chassis back over, we need to fit the pivot beam into position -