Looking for advice on tyres - my newley aquired DT 400 still has the original tyres from 1976 fitted to it so clearly need replacing.

Most of my riding will be on the road so not really looking for off road tyres - been thinking that Continental - Conti Go might be a good choice but would appreciate any recommendations.

I've been searching for affordable tires (would like to get the Heidenau tire but out of my current price range), so here's what I've come up with, since most manufacturers don't make matching tires to fit out bikes... 

Duro HF307 TRIALS TREAD MOTORCYCLE TIRES

For the best factory look at a decent price I use IRC Trials. No need to spend the money on Heidenaus (I use those when I need a 19” front tire). The 76 400 uses a 21” so more options out there. Look at the IRC Trials.

I'd like to buy the IRC but can't find the correct 3.25-19 front tire.

I already answered that? The 76 DT400 uses a 3.00 x 21” tire not a 19” tire. Maybe you are working on a different bike? 

You'd be right if I was talking about my 76 DT400 but I'm searching for my 72 DT2, guess I didn't make that clear - my fault...
 

You are right my DT400 does have a 21" front wheel / 18" rear.

I have managed to find some road based tyres that will fit both both front and rear, they are Avon Road Rider MK2 - these will be ideal for me as all my riding will be done on the road. Another alternative are Biddgestone Battlax tyres.

As you may know I am based in the UK and Avon tyres are readily available.

lol you literally opened the question with “my DT400 has the original tires…”

You might look at the Shinko SR 241 tires also, that's what I was planning to run on my '75 DT250 when the originals wear out.

They offer the various sizes we need for the classic enduros, including 19" and 21" fronts. They also match the original Dunlop look very closely.

I've run various Shinko tires on other bikes and they are good. Basically they are the old Yokohama tires being produced in Korea.