The #143 heads came on 1967 290 HP 400 engines, factory compression rated at 10.5:1. In actuality it will be about 9.75:1 or 10:1. That much compression might be pushing it for pump gas operation.
The press-in rocker studs on your heads may not be too happy with the fast-acting cam and the valve springs you have chosen.
Another problem is the '72 pistons have valve reliefs that don't match the valve location and angle on the #143 heads. In mid-'67 the head design changed, your heads were made before that change occured.
My take: Find some different heads.
Yours have too much compression, press-in studs and the wrong valve angle to match your pistons.
The press-in studs will pull out in time. The valves may hit the pistons. The engine may suffer damge running pump gas on 10:1 compression.
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1964 Tempest Coupe LS3/4L70E/3.42
1964 Le Mans Convertible 421 HO/TH350/3.08
2002 WS6 Convertible LS1/4L60E/3.23
1966 VW Type 2 Single Cab Pickup 140hp 2276
1956 VW Type 2 Panel Van 36hp 1200
1957 VW Type 1 Beetle 180hp 2276
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