Step 1
Widen the block at the bust, lower the armpit, raise the shoulder and take the armhole a bit outwards for the 80s shoulder pads.
Work on the sleeve in the matching way and raise the sleeve cap by the same amount.
Reduce the sleeve hem and extend it for the gathered effect.
On both front and back redraw the neckline, while on front only draw the slash lines that you see marked in red.