Fill that whole in the transom, get a bracket and I'll sell you my 88 SPL that's in excellent condition to put on the back.
We did that with a friends boat. Mercruiser with south, outdrive needed to be rebuilt so he had the whole filled for about $350 and found a crashed bass boat with a Johnson 175 and bought it and the jackplate for $2000. Has been running it like that for 5 years. He made a bench seat and turned the engine bay into storage and an ice chest with a bilge pump to suck out the water when the ice melted. Works perfect for him.