For a fair bit less than $5K you would surely be able to pay a mechanic to source you a good condition second hand engine and gearbox and do the manual conversion for you.
But for $5K, you would also be able to go and buy another manual U13 SSS in reasonable condition..... Then use your old car to swap over all the good / better bits and make 1 good car out of the 2.
decisions, decisions.....