Check out Fordsix.com. You will find them a very nice group of guys and very informative on the Ford 6's. There is info on an alum crossflow head for the 200 block and other parts. A 300 bb inline can be made to fit - be different.
Going to that forum would be a mistake. Many of the original moderators from that forum are on this forum or mustangsandmore including myself.
Either fix your 170 if its fixable or go to a 200 six.
Using a 300 six instead of a V-8 is insane.
Remember if you are going back to close to original using a six with no mods do it.
However if you plan to not go back original, find a V-8 doner vehicle & get all the upgraded suspension componets as well as driveline & V-8 mounts.
Going to a V-8 is your best move unless you just want to keep the original six in stock condition.
Remember if you go to sell the vehicle the V-8 vehicle will bring twice the money.
Another problem with the six cylinder engine is lack of decent quality parts.
To get a decent distributor gear for the six you have to get one from australia.
How do i know i have gone that route & could have built a 347" small block for the money i pissed away on a six & having three times the power.
The fordsix forum has chased away more talented moderators & members than it has kept.
If you need some steel shim headgaskets for the 170" engine i have them for sale. Make the right choice from the beginning.