Only cars exported to the US had narrow port heads, these being fitted to TR250 and early TR6 both with the commission number prefix CC. It is the inlet ports that are different in this respect, the exhaust ports are the same throughout.

All TR5 and all TR6 other than CC prefixed cars have a wide spacing of the inlet ports. If you are considering changing your cylinder head, adding an extractor manifold or fitting a carburettor manifold, including Weber manifold it is essential to know which head you have.

To find out, measure between the inlet ports which are in 3 pairs.

CC cars: 17mm. The gasket usually has slightly larger diameter holes therefore the gap in the gasket will measure 15mm 

CP, CF and CR cars:  25mm. The gasket usually has slightly larger diameter holes therefor the gap in the gasket will measure 23mm

Note: - Many TR's have engines and heads from saloon cars fitted  so measuring is the only sure way.