Welcome to the forum Gibby !
Maciej make them for GT150's , he might be able to make graphic / plate for the V156.
You will need a good picture of one, for him to make one if he hasn't reproduced one yet.
Are you on Facebook ? You can contact him there .. Or I can ask him.
His contact here and on eBay ..
http://forum.cgoamn.com/index.php?topic=2694.0His Facebook group …
https://www.facebook.com/groups/glastronGT150/If he can't .. Try Aaron here or on Facebook
http://forum.cgoamn.com/index.php?topic=7978.0You can also search eBay for other company's reproducing them.
If your transom is solid, you could put a 115 HP motor on it. Everyone put's 115 HP motors on the GT150's.
After you remove old motor poke around in bolt holes for soft wood.
You will need to drill new holes for the J/E motor, old Merc were different pattern.
Might want to check with your insurance company first, if you carry insurance.
Best picture I have of plate from 1972 V156.