Transmission Cooler

Wayne Miller said
1962 Dodge Lancer Wagon slant six.
I am cramped for space by the exhaust and motor mounts etc to run cooling lines up to the radiator.
Will this cooler provide enough cooling for a 904 if I place it under the floor measures 6"X12View attachment 1715731416Just using natural air circulation.

Absolutely Not!

As has been mentioned, the one you've pictured and many others utilize natural airflow to augment their cooling capability and should be mounted in front of the radiator. Its typical for exhaust and motor retrofits to decrease access and usable space but these issues can always be overcome by just analyzing the obstacle, using a little creativity and finding a solution which is usually available right off the shelf. In your case that means either bending some new hard lines or using flexible lines which is what I've done on my latest project with braided hose and AN fittings. I'd show you how I've routed mine but the motor bay and front end undercarriage is all apart for the next couple of weeks.

Without a pic of your undercarriage and the coolers type of termination fittings, its hard to suggest how to plumb and route it but rest assured you've got options.

***They do make coolers that are specifically made for mounting in locations where airflow is limited or not available but they have their own self contained fans built into the unit.