http://www.highwaymarine.com/ Mark- these guys have an online microfiche for Mercruiser, if thats the drive system you have. Just scroll thru the engine list till you find small block Chevy(262 thru 350 cid), the front mounts are listed under "engine mounting", the rear mounts will be found under "flywheel cover". Something to consider is checking over several year/displacements, many times things like engine mounts will interchange between them(check part #s)especially if all you need are the isolating rubber parts. One other thing to consider is that these mounts/bushings may need to be pressed out or into the brackets, easy if you have access to a press, challenging if not! I had to do a lot of research on this for a 3.0 mercruiser in a 70 Seacraft cc.
Good luck,
Pat in MD